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FAQs about Overflows, Bulkheads/Through-puts, Stand-Pipes, Holes vs. Boxes... Sizing, Number, Placement 1

Related Articles: Overflow Box Arrangements, Plumbing Marine Systems by Bob Fenner, Myth of the One Inch Beast (Why Relying on One Inch Overflows... or Overflow! Is foolhardy) by Scott Vallembois, The Flowrates through various Bulkheads (In relation to overflow drains) by Scott Vallembois, Plumbing Return Manifolds, Refugiums

Related FAQs: Through-Puts 2, Through-Puts 3, & Overflows 1, Overflows 2, Overflows 3, Overflows 4, & FAQs on: Rationale/Use, Through-Hull Fittings, Hang-On Selection, Plumbing, Troubleshooting/Repair... Marine Plumbing 1, Marine Plumbing 2, Marine Plumbing 3Marine Plumbing 4, Marine Plumbing 5, Marine Plumbing 6, Plumbing 7, Plumbing 8, Plumbing 9, Plumbing 10, Plumbing 11, Plumbing 12, Plumbing 13, Plumbing 14, Plumbing 15, Plumbing 16, Plumbing 17, Plumbing 18, Holes & Drilling, Durso Standpipes, Make Up Water Systems, Pumps, Plumbing, Circulation, Sumps, RefugiumsMarine Circulation 2, Gear Selection for Circulation, Pump Problems Fish-Only Marine Set-ups, Fish-Only Marine Systems 2, FOWLR/Fish and Invertebrate Systems, Reef Systems, Coldwater Systems, Small Systems, Large SystemsWater Changes Surge Devices

Mega Flo... Not!
Better to DIY...

Hi Bob, 

I am just about to drill my aquarium and add a trickle tower and I just wanted to know whether there are any benefits to having the overflow in the middle of the aquarium or on the side? The aquarium will be against a wall so not viewable from all sides and because of this I am leaning towards having the tower in the center. Any advice would be appreciated. 

Many Thanks
Simon Heynes 

            Glad to assist you Simon. There are a few benefits from arranging overflows in any location, but my fave are in the upper corners'¦ Everything else being equals (rarely the case); these areas are structurally sounder to make through-puts. Additionally, it's easier by far to arrange circulation at one distal end of a system and drive currents to the farthest point or downward and about in a gyre, w/ optimizing circulation and arranging more complete turn over in this way'¦ Lastly, my take on aesthetics of tank engineering: I really don't like seeing these plumbing arrangements, and they're far easier to disguise in the corners. 

            IF the overflow/s has/have to be placed in the center this isn't really such a big deal functionally or for looks in any case. What is far more important that there be redundancy in the number and diametre (size) of said drains; should one clog for whatever reason.

Plumbing Pumps & Holes   12/14/06 First of all thank you for your time, patience and knowledge. I am planning my tank order and I would like to get it right the first time. Here goes... 180 glass (72x24x25) Looking for about 15x turnover (3000gph) with the following. Two 1.5 inch drains in the back wall draining into a 75 gal refugium. A mag18 returning over the back with 2 outlets, should be around 1000ghp. Also a 2 inch drain driven by a Dart attached to a closed loop. The loop will be over the top into an inside perimeter manifold with about 4 outlets, <I'd double this number> should be around 2000gph. Will a 2 inch drain feed the Dart. <Mmm, barely... if it were me, mine, I'd also double this number of intakes, join together near the pump intake... for a few reasons... but mostly for the inevitable blockage near, over one of them> Does this sound  like a good plan for my flow target. Many thanks in advance. Daryl <Bob Fenner>

Re: Plumbing Pumps & Holes   12/15/06 Thank you for your time, you/yall are a great asset.  Holes side by side, maybe 6 inches apart? <Mmm... intakes? At either endish... Please read here: http://www.wetwebmedia.com/plumbingmarart.htm and, oh yes.... the linked files at top. BobF>

Upgrading after a year    4/4/06 Hello people!!  I've had a 70 gallon saltwater aquarium up and running now for a year and now its time to upgrade.  The plan is for a 72"l by 24"w by 22"d, what is that about, 150 gallons? <Yes> For drilling the holes I've decided to drill 5 one and a half inch holes across the back top pane of glass, 2" from the top and 2" from the sides, spread evenly across.  3 will be overflows going to a 50 gallon sump and 2 returns to the display tank.  Does this sound ok so far? <Yes... but I would make the drain holes two inch... to accommodate 1 1/2" through-put diameter> The glass is 3/8",bottom piece is 1/2" thick.  Could you tell me what the best size pump to get for this would be (GPH)? <... posted on WWM> The sump will be directly below the main display tank if that makes a difference.  Thanks for now for your wisdom!  Steve K <A bunch more to go over Steve... That you may already know... But do read on WWM re plumbing, through-hulls... Bob Fenner>

Drain Line Confusion  4/29/06 Hello all! I'm about to have my tank drilled by an LFS and seem to be having a bit of conflict as in the amount of drain lines I need. I had planned on having two 1.5" drains drilled in my 75 gal. but he's trying to get me to only go for 1 2" drain. <You're better off with the two 1.5"> The holes will be on the back as the bottom is tempered. His reasoning is that the 2" can handle the flow from a 1000 gph pump and less holes means stronger glass. <A reasonable statement, however, there will be much better circulation afforded by having two distal overflows, and a margin of safety granted should one become occluded...> This makes sense but at the same time I am worried that the single 2" drain will result in a noise issue. Are my concerns valid? <Yes... though pi R squared for the surface area of both... The two lines can be about as noisy if not engineered properly> If I can should I get him to agree that if I do have issues with noise he will drill another hole without me spending more? <Mmm, up to you, but it's a pain in the keester to take the tank back down and into the shop... if it were me, I'd just have the two holes drilled and be done with it> (the deal is he'll drill and build an overflow for $125) Looking forward to your response. Joel F. <Bob Fenner>

-Sand and bulkheads-  - 5/7/2006 Hello crew!  I have two situations today that I hope you can help me with. <Certainly>       Situation number 1:  I'm starting up (another) new tank, and I am using Nature's Ocean fine sand (not live sand).  I didn't realize it until I had already added it, but I'm supposed to rinse this stuff.  Now the water's all cloudy and full of gunk.  Will this settle in a day or two, or do I need to empty the tank, rinse the sand, and start all over?  I don't have enough salt at the moment to do that, so I'd half to wait a day or two regardless.  Maybe running a filter on it would help? <The sand "dust" will settle within a day or so, and running an extra filter will help clear up the tank, just check and clean your pumps powerheads etc after it settles to ensure they are not clogged with dust either.>       Situation number 2:  I had a tank (yet another) drilled for bulkheads.  One 1.25 drain (was supposed to be 1.5 but they got it wrong) and two 1" returns.  Now I see that all the bulkhead sizes appear to be too big.  One inch seems to mean "inside diameter" and my holes are only 1" so...what can I do?  Do I just have to take this back and get it re-drilled?  It's pretty expensive here (most places charge $30.00/hole).  I'm hoping you know of a place online that sells special small outside diameter bulkheads (remember -- MUST fit through a 1" hole).   <I do believe that a 1.25" drain is a 3/4" bulkhead fitting.  my slightly bigger All glass aquarium one that came in a kit, was about that size.  If you can, I would look into having the hole redrilled and get the people that did it wrong to redo it if possible.>      Thanks bunches guys!  We really appreciate your help out here in cyber-land. Angelica <Hope that helped> <Justin (Jager)> Bulkhead misery - 05/06/2006 I recently got my 75gal AGA tank back from my LFS after having him install a custom overflow as well as drill the back for a bulkhead. I had told him I wanted a 2" bulkhead and that's what he put down for my order and that is what it says on my receipt. However, upon getting my tank back, whoever drilled it only put a 1" bulkhead on it. <... bunk> I was in such a rush at the time I got it, I didn't have a chance to discuss this issue with the guy. Now I am trying to decide if it is worth the effort to get him to fix his problem, or if there is anything that can even be done to 'save' my tank. <Mmm, can be re-drilled... otherwise refit> First, I know I have every right to demand (or ask politely, haven't decided how angry I am yet) that he fix his error. <You are wise to "hash through" w/ yourself, not be angry, emotionally distraught in dealing with this/all matter/s> I just need to hear someone else tell me it's the right course of acting and is worth all the hassle! Second, is it possible for this overflow to work with my setup which will have a 1190gph pump returning water to the tank. <Mmm, no... the present through-put will not accommodate this flow> According to reefcentral.com's head loss calculator I will have appox. 890gph when all is said and done. I know this is cutting it close, but is it better than the alternative of taking it back to get it fixed. <Not IMO... better to have re-drilled. As important as adequate diameter of this fitting, plumbing is, there is also an/the issue of noise... much easier to correct with bigger...> I know only having one overflow is a danger in itself, but I thought that having the 2" drain line would reduce the risk significantly and now that it's only 1", my gut is churning. I guess I know that getting it fixed is my only real option here if I want to avoid disaster. This makes my real question what can be done to fix this by the LFS? The overflow is a 3 sided trapezoid on the middle back of the tank with the bulkhead in the middle of the height of the tank, about 10" up. Could another bulkhead be drilled below/above the existing one so that one acts as a backup? <Yes...> Your suggestions that I can take to the LFS would be greatly appreciated. Up until now I loved this particular aquarium store, but now my experience is soured by this episode. Thanks for listening to my tale of misery, Joel F. <Mistakes happen Joel... do take this up, patiently with the stores management... asking what they might do, suggest to remedy the situation. You do need more through-put here. Bob Fenner>

Re: Bulkhead Misery, And fluorescent lambda - 05/07/06 Hey Bob, <<EricR here...Bob's off at another "fishy" event>> Took the tank back in today after talking with him on the phone. He's just going to redrill and fit a new 2" bulkhead on there. <<Great to hear>> He was really apologetic about the whole fiasco.  I'm just glad it was so easy. <<Indeed... As Bob stated, sometimes best to "cool down" and present in a calm manner>> On another topic, I am trying to determine what type of lighting would be better for my setup.  I was going to go with 4 x 110watt VHO's with 3 being 10k and one being Actinic, but I've also had reefers suggest T5 HO's. <<The current "fad"...the VHOs will be just fine>> The cost for T5's is quite a bit higher from what I've seen and it seems I would also need more like 6-8 T5 bulbs. <<Agreed...VHO gets my vote/is what I use/have used for years>> As far as what these will be lighting, I plan on keeping mostly softies and maybe eventually some LPS or SPS and a Tridacna derasa.  Which would be more appropriate for this? <<Not saying the T5s wouldn't work as well, but I have a good friend who keeps all the critters you mentioned under VHO lighting with great success>> Thanks again, Joel F. <<Regards, Eric Russell>> Refugium, Pump, and Overflow Sizing - 05/17/06 Hi, <<Hello!>> Have been doing much research on reef tanks, mostly on the web and came across your site, what a find, very impressive. <<Thank you>> I just bought a 100 gal DAS reef tank.  It's got a single 1-1/2 inch sump drain in a corner.  I wanted to put the large CPR Aquafuge under it and use an external 1000 GPH pump for circulation with a SCWD wavemaker. <<Mmm, which model Aquafuge?  Unless you're talking about the "Aquafuge Pro" it is too small/not really suited to this application.  It would be better/cheaper to employ a small aquarium (20g/29g) for this>> My questions are - 1) Is the pump too big for the drain? <<My opinion?...yes.  Most overflow "calculators" will tell you you can get 1200/1300 gph from a 1.5" drain.  And under "ideal" conditions maybe so...along with lots of noise and continuing fuss.  But tank conditions are rarely ideal...plumbing is not always optimized...and there's the fact the plumbing will slowly become more restricted from mineral/biological buildup.  I think it is much less problematic to "tune" your overflows when you only try to push "half" the rated flow.  That leaves you in this instance with a pump that will push 650 gph or less (after determining/calculating head loss) to the overflow>> 2) Is the refugium big enough? <<Depends on the model>> 3) Is 1000 GPH too much flow through the refugium & if so how would you control it separately? <<With a smaller pump...perhaps a Mag-Drive 9.5>> And lastly;  4) Is the skimmer that comes with the CPR any good? <<I think you will be disappointed.  I would replace this...look to ASM, AquaC, Euro-Reef, others...>> Thanks in advance for any help. <<Very Welcome, EricR>>

Overflow Bulkhead Size? - 05/25/06 Hi, <<Hello>> I was wondering if you could shed some light on the subject of the overflow hole size. <<Sure>> I recently ordered a 135 gallon glass tank w/overflow.  The drain or overflow is 1" and the return is 1/2". <<Mmm, typical...and "undersized" in my opinion>> A local fish "expert" told me that I need to cancel the order and get at least a 2" overflow hole? <<If possible, I agree>> Why is this? <<The larger throughput will make it MUCH less problematic to plumb this tank with regards to noise, maximizing flow, etc.>> I do not understand why it matters and I already purchased a ProClear Pro Series wet/dry 150. <<Please read through our marine plumbing article/FAQs, there is much helpful info...you can start here: http://www.wetwebmedia.com/plumbingmarart.htm >> I thought this was going to be a good set up.  Am I wrong? <<Can't say for sure, I don't have enough information about your setup or what you plan/want to keep>> Also, he said the glass tank will not hold up with 2 holes drilled in it?  Confused? <<...?  If the tank is properly constructed with forethought to hole size/location, multiple throughputs should not be a problem>...perhaps you need consider another tank manufacturer> I appreciate any info. Thanks -Dan <<Regards, EricR>>

Regulating Pump Flow... Inadequate Factory Overflows - 06/12/06 Hi Crew, <<John>> I bought an Eheim 1262 to use as the return from my sump to my 90g (with AGA Megaflow). <<I love Eheim pumps...wish we could get some of the bigger ones over here>> It's a great pump, but it seems too powerful for the Megaflow system. <<Not so "Mega-", eh?>> Actually, I should say it seems too powerful to run the Megaflow quietly - water rushes though the system and it sounds like a dishwasher. <<Typical of these undersized (Mega or not) factory overflow systems>> I've read through the FAQs and this seems like a common problem. <<VERY common>> One suggestion that helped was to increase the diameter of the hole at the top of the Megaflow drain tube.  However, my system is still extremely noisy, unless I pinch and restrict the flow coming out of the Eheim. <<Replacing the Megaflow drain tube with a Durso-style standpipe might allow both an increase in flow AND a reduction in noise...but still no replacement for the simple want/need of a larger throughput>> So my question is (finally) is it safe to add a ball-valve on the return side of the Eheim, or will this produce too much back pressure and jeopardize plumbing connections? <<This is quite safe and satisfactory, though I would install a gate-valve as opposed to the ball-valve for better "finesse" of the flow.  Magnetic drive pumps such as the Eheim respond to/endure this type of control/adjustment very well.  But do make sure you install the valve on the "output" side of the pump>> Would it be better to step down to the Eheim 1260 and let it run unrestricted? <<Not in my opinion.  The plumbing lines will eventually start to restrict from bio/mineral accumulation...but with a twist of the valve you can step up flow to compensate>> Thanks, John H. <<Quite welcome, EricR>>

Optimistic Flow Rates - 07/11/06 First of all great website, I've learned tons and spent hours reading posts, thank you. <<You're quite welcome...glad you find the site beneficial>> I tried to find my question but had no luck. <<Let's see if I can help>>>> I have a 300 gal FOWLR with a 50 gal sump.  I am running two twin tube hang on the back overflows, both with twin 1" drains.  I read I should be gravity feeding 1200 GPH for each box totaling 2400 GPH to my sump. <<Read?  Where?  No way on Earth you're gonna get 1200 gph to "gravity flow" through a 1" drain.  1200 gph may be the "rated" flow on the overflow boxes...but it's not going to happen with a single 1" drain>> My return pump is the Mag 2400.  I want high flow as I have groupers and triggers in this tank. <<Mmm, yes...most all fish species appreciate good water flow.  Though I'm skeptical when it comes to processing this much water through a sump.  But if the noise, bubbles, splash is not an issue with you...>> I used 1" for everything. <<Not big enough>> Right off the pump I have a check-valve, spring type from Lowes and a ball-valve on top of that all in the return line. <<The check-valve is not a good idea.  Aside from metal contamination from the spring and the huge lose of flow incurred when using these devices, the valve will inevitably fail at some point...usually when no one is around for a long period.  Much better to adjust your skimmer boxes, return lines, and the water level in the sump to handle all transient water when the power is off.  I'd also like to suggest you replace the ball-valve with a gate-valve...will give you much more "finesse" when flow adjustment is necessary>> Then it goes up the back of the tank and tee's to the ends when I have a 90 up then a 90 over then a 90 down and a 45 into the tank. <<Mmm...head pressure indeed.  Between the check-valve and the elbows I doubt your getting little more than half the rated flow of the pump>> I hope you can picture this. <<I can>> The problem is even with all that head pressure from 10 90-degree fittings, the ball-valve and the 45-degree fittings, I can't run the pump at even 50% or the aquarium overflows. <<Not surprising.  At the "most", I think you should expect 500-600 gph from the 1" drains...about half that if you want a bit of a "safety margin" or to keep things quiet>> I have to turn the ball-valve closed by almost half way for the tank to not overflow. <<Indeed>> Will changing the return plumbing to 2" help fix my problem? <<Ahh yes!  Will improve things by a huge margin>> Very confused, and lots of different formulas and theories. <<Agreed...and most seem a bit "optimistic" to me where flow rates are concerned>> Please Help. Thank you, David <<I hope I have.  Regards, EricR>>

Optimistic Flow Rates II - 07/11/06 Ok, I was told by US Plastic's that a 1" drain will flow approximately 600GPH. <<Yes...hear this all the time.  But I can tell you a more practical expectation is about half that.  A 1" drain may indeed be "physically capable" of allowing a gravity flow of 600 gph...getting it to work so in an aquarium application is another matter>> My overflow boxes have dual 1" drains.  That's where I figured 1200GPH per overflow box. <<Oh, okay...did not get that from the first email>> Four 1" drains for a total of 2400 draining to the sump. <<I see now.  But as you have discovered...not a practical flow rate>> The bottom of the overflow box has a 1" union going through it. <<Not a "union", is a "bulkhead"...two different fittings>> So do I need to try and drill a bigger hole in the bottom of the overflow box to accommodate for a bigger bulkhead or can I just adapt a 2-inch pipe to the 1-inch bulkhead. <<To increase the flow rate you will need to increase the size of the throughput (bulkhead fitting and drain pipe).  Just adding a larger pipe to the 1" bulkhead won't help, it still leaves you with the smaller restriction at the bulkhead>> I also have the 1" U tubes.  Do those also need to be bigger? <<Likely bigger AND more of them.  Actually, you might try this first.  With all the head pressure on your pump, the four 1" drains may well handle the flow and the real problem is your siphon tubes are not keeping up>> And worst case if I can't drill the bottom of the acrylic box to adapt for a bigger pipe, can I just add another dual-drain overflow box? <<If there's room...certainly>> Then not only would I have a plumbing nightmare, but I'd have SIX 1" drains going into my sump. <<You may want to consider alternative methods for creating flow and assign a smaller pump to service the sump>> I would like to keep the high flow rate as it seems to make a difference in my other salt tanks. <<I would agree, but it doesn't all have to be processed through the sump. Not having a drilled tank makes a closed--loop problematic...perhaps some Tunze Stream pumps?>> I never imagined this to be this complicated. <<Designing/building the drain system can often be challenging>> I greatly appreciate the help in your fast response. Thank you <<Very welcome, EricR>> New Display-Questions on Bulkheads/Sumps/Filtration - 07/21/06 Dear WWM Crewmember, <<EricR here...how can I be of service?>> I have been a freshwater aquarist (125 gallon) for many years and am now taking the leap to marine. <<The experience will serve you well...but still, much reading/research ahead of you>> I have researched your excellent site and read through The Conscientious Marine Aquarist. <<A good start, but don't limit your research to a single source.  Opinions/experience is varied and wide.  Gather your information from varied sources and use your own good judgment to make decisions re>> I have learned tons but still have a few questions regarding my specific needs. <<Alrighty>> I am interested in purchasing a 175 gallon Oceanic bowfront w/ two MegaFlow overflows (rated at 650 gph each, for a total of 1,300 gph). <<Mmm yes, generally undersized and overrated overflow systems.  For simplicity of plumbing/maintenance, and to ease noise/bubble issues, I would plan on/expect about half the rated flow>> Although I intend for it to be a FOWLR set-up, I know one day after much experience I may want it to become a reef tank and want to plan accordingly for flow. <<Yes, best/easiest to plan/plumb at this stage>> Not to mention I'd also like the flow increased for the FOWLR set-up anyway. <<Indeed...vigorous water flow benefits fish as well as coral>> Therefore, when placing my tank order from my LFS I am going to have Oceanic drill larger bulkhead openings. <<Ah!  You "have" been doing some research!  Excellent my friend>> It comes standard w/ holes large enough for 1" outlet and 3/4" return inlet. <<Yes...unfortunately>> I'm hoping the MegaFlow overflow is large enough for holes sized to accommodate 2" bulkheads.  Do you know if this can fit in their MegaFlow overflow? <<Mmm, don't know...perhaps you can order these "upsized" as well>> What about increasing the 3/4" return inlet if it fits within the overflow - should I do this as well? <<I would, yes (1").  Can always be "necked-down" at the tank if you need more "velocity">> Any bulkhead size recommendations for this specific overflow would be appreciated. <<As big as you can go with the current overflow box...or upscale the overflow box>> On to sump/refugium questions... <<Okay>> I am planning on purchasing a 55 gallon capacity sump/refugium from S P Aquatics... <<No chance of separate vessels for these?  Using a single vessel for both can be/is done by many, but generally one methodology (sump or refugium) or the other suffers, in my opinion.  But I find separating the two eases equipment placement, attenuating flow for each, maximizing space, etc....and greatly simplifies isolating one from the other when/if necessary for maintenance/repair>> They have two designs (or will customize) and I have no idea which might be best for my set-up.  The "X1" models have the display drain area on one side, water moving through refugium in middle, then water moving to skimmer/return area on the other side. The "X2" models have a display drain/skimmer area on one side, another display drain/refugium area on the opposite side, with both sides flowing water to a middle return area.  Any ideas on which one might be best? <<I think the "X2" is the better design...less chance for the skimmer to "rob" you of beneficial organisms from the refugium>> I plan on using a EuroReef CS8-3 skimmer. <<Ahh, wonderful...I love these skimmers...use a CS12-3 myself>> Also, in addition to the skimmer, I'll use live rock in both the tank and refugium - should I employ wet/dry filtration in this sump as well? <<I wouldn't, will consume a lot of space which will already be at a premium as you'll discover.  Obtain and use a fluidized-bed filter...great for FO/FOWLR systems...will ramp-up/adjust quickly with fluctuating bio-loads.  Will also be much easier to "disengage" than a wet-dry when the time comes>> Your help is much appreciated - thank you. Martin <<Happy to assist.  EricR>>

Drain Flow Rate 9/27/06 Howdy guys and gals! Thanks very much for all the help so far! <Hello Garth>    My new tank has a corner built in overflow box with a 50mm (2") drain hole drilled in the bottom. with two 32mm (1 1/2") pump pressure returns drilled holes. The drain return (to the sump) has a bulkhead fitting and due to that it ends up with 40mm (1 1/2") ID PVC pipe and a Durso submerged inlet (all 40mm - 1 1/2") The pump pressure returns are also bulkhead fittings and end up as a 20mm (3/4") ID after the bulkhead fittings. But with the use of an adaptor I end up with 1" ID for the two pump pressure returns. I plan on running two Oceanrunner OR2500 rated at 2500l/h each (625gph). <The OR2500 is rated at 650gph.> There will be approximately 4ft head  on these two pumps. So I will have a total of 5000l/h (1250 gph). <With a four foot head on each pump, you will not have 1250gph, but somewhere around 700-750 gph which is well within the drain's capability.> I would just like to know if my overflow will handle this flow rate. Thanks for your kind words of wisdom. <James (Salty Dog)> All the best and take care. Garth

Re:  Overflow And Pump Size 9/27/06 Hello again James, Thank you for the quick response. <You're welcome.> In regards to connecting the sterilizer and chiller on the same pump, I had posed this question earlier on WWM. The chiller I have has a flow rate of 250-350 gph and the sterilizer a 100-200gph flow rate. EricR (who responded quickly as well) said that I should use separate pumps for each since trying to adjust proper flow would be difficult. Do you still think I should connect them all together, if not, do you still recommend a return pump of 500gph. <You gave no flow rates on the equipment in your query to me, so I assumed they were sized for somewhere in the 300-350gph range.> (I am adding EricR's response so you can see it in total.) <Should have replied with Eric's suggestions, since he answered your original query and was aware of the equipment being used.  Much better for the same person to do the follow-up.> I value everyone's opinion at WWM so any suggestion on which method to use will be greatly appreciated. I want to try and avoid  the whole "trial and error" process as much as possible. <Now knowing the equipment you have, I would go with Eric's suggestion on the UV, and, if it were me, I'd go with a pump in the 400gph range and pump water from the sump, into the chiller, and back to the tank.  With the head pressure loss, you will be around 275-325 gph on the return, well within range of the chiller recommendation.  Additional flow rates can be increased in the tank by use of a powerhead.  This will give you flow in the tank from more than one direction.  Based on Eric and myself's suggestions, you will have to decide which method will work best in your situation.> Once again thank you in advance. <James (Salty Dog)> Wayne Overflow And Pump Size 9/26/06 Hello, <Hello Wayne> I am planning on upgrading my 15 gallon tank to a 35g with a 20g sump. My  tank is not drilled so I'll have to use an overflow to bring water to the sump. What type of overflow do you recommend (gph flow) for this size of tank and what gph pump do you suggest. I am thinking about using a SCWD wavemaker connected from the return pump. I will be connecting a 9w sterilizer and a 1/10 chiller into the sump as well. Each  will have its own pump because of the differing water flow. The chiller and sterilizer will be pumped from the pumps in the sump back into the sump ( if that makes any sense). Only the return pump will be returning water back to the tank. Is this method of circulation o.k. or should I try it another way. I will have a skimmer, but due to the limited space in the sump it will have to be hung on the back of the tank. Keep up the good work. <Wayne, not a very good way to do is.  First off, the chiller will be turning on/off constantly as it will be looking at water already cooled for the most part.  Same goes for the UV, you want it to look at as much tank water as possible.  I'd select at least a 500gph pump and connect everything in-line.  Pump through the chiller, then the UV, then back to tank.  Multiple pumps in a small system will use more energy and create more heat, and the chiller will run more often, adding to the bill.  Overflows should be selected so that it's total flow rate is close to the pumps capability.  Oversized overflows create problems in this regard, often leading to constantly removing air trapped in the "U" tube due to the slower flow rate through the tube.  I'd probably go with the CPR CS-90 overflow, which will give you a maximum of 600gph flow rate.  This still puts you in between a rock and a hard spot.  The CPR CS-50 is a little shy on flow rate for your tank (300 gph), and the CS-90 is a little high at 600gph.   Your other option is to have the tank drilled, which would be the way I'd go.  It would still be cheaper than buying the overflow and eliminate the hassles of such, and less clutter in/on the tank. The 20 gallon sump would still be fine in this system.> Thanks in advance. <You're welcome.  James (Salty Dog)> Wayne

Overflow Design/Bulkhead Size    10/3/06 Hello. <<Howdy>> I have a 135 gallon (6-foot) glass aquarium that is not drilled that I would like to set up as a reef. <<Ok>> After doing some reading on your site I'm leaning toward having the tank drilled and building some sort of gravity fed overflow, since siphon "CPR style" overflows seem to eventually fail. <<Indeed...though I must admit I ran/used siphon overflows for more than a decade with but a few "failures" in that time... and nothing catastrophic as I always allowed for transient water volume in both sump and tank.  There are measures to take to increase reliability...and if using siphon overflows it is always a good idea to use "two".  But if you can drill this tank then I do suggest that is the way to go>> I like the idea of drilling the holes on the back wall near the top of the tank (2-3" from the top would be ok??) in case a bulkhead leaks not all 135 gallons end up on the floor. <<Mmm, yes...is my preference over drilling the bottom as well.  As for the holes, the edge of the drilled hole should be located at least the diameter of the hole away from any edge (top or side).  For example...a 1 1/2" bulkhead requires a 2 3/8" hole, thus, the hole should be located so it edges are no closed than 2 3/8" to any tank edge.  This is a bit conservative for some folks, but is a good rule of thumb for maintaining/maximizing strength/integrity of the glass panels>> I was planning on 2 X 1 1/2" (inside diameter) bulkheads, would this be sufficient for approximately 1,000gph flow from the sump pump? <<Should be, yes...and why not drill an "extra" bulkhead while you're at it?  This can be capped-off for now but will be available should you decide to add a closed-loop, etc.>> Is it necessary to attach the internal overflow boxes around the bulkheads or could I just use some sort of basket shaped screen to keep critters from going through the hole?  The screen idea just seems much easier. <<Indeed it is.  I have my tank drilled through the end walls (is an in-wall installation viewable from front and back).  I used "slip" bulkheads and modified 1 1/2" ABS 90-degree ells (notched edge of top opening) fitted with a short length of PVC pipe and inserted in to the bulkheads to create "mini" overflows.  Another method would be to simply insert bulkhead screens and design the drain plumbing coming from the bulkhead to the sump with a small "hump" just off the bulkhead to control/raise the water height in the tank above that of the bulkhead.  (Have I lost ya yet?)>> If I did decide to build an overflow box do I have to use glass since nothing seems to permanently bind glass and acrylic? <<Silicone will usually bind acrylic sufficiently for in-tank overflows>> Is there anything else I could build it out of that would bind to the glass aquarium that is easy to cut and work with? <<Give the acrylic/silicone a try...many overflows in manufactured tanks these days are plastic>> Ok, one last question.  All the overflow boxes I have seen in stores always go from the top of the tank to the very bottom. <<Generally because these tanks are bottom-drilled>> I'm assuming this is because they are made for tanks that are drilled at the bottom. <<Ah, yes!>> Since I want to drill my tank near the top, can I build a much shorter overflow box, say 5-6 inches tall? <<Indeed you can, though without support from resting on the bottom of the tank, glass might be a better choice over acrylic for the better "bond" with the silicone>> What would you recommend as the minimum dimensions of each overflow box to accommodate a 1 1/2" (inside diameter) bulkhead? <<Hmm, I'd try 5" high x 4" deep x the entire length of the back wall...but do a Google search on our site/the NET re "horizontal overflow" to get other perspectives on this>> Thank you for all your help, Jon <<Happy to assist.  Regards, EricR>>

Re: Overflow Design/Bulkhead Size -- 10/03/06 Eric, <<Jon>> Hey, thanks for all your help. <<My pleasure>> I really like your "mini" overflow idea. <<Works for me <grin> >> Is it very loud? <<Nope>> I read that many people install the "Durso" standpipes to quiet the water. <<Tis is true but there are others ways to mitigate noise...reduce flow or increase the number of throughputs for same...aspirate the drain lines...>> In your "mini" overflow design, I don't think that is possible, is it? <<Would/is not possible, no>> Is that a problem? <<Not in my experience/with my configuration>> Would two 1 ½-inch diameter elbows acting as the mini overflows be sufficient for a 135 gallon (1000 gph flow)? <<Can't say for sure without giving it a try but yes, likely so if you can aspirate the lines well enough to prevent surging/sucking.  But honestly, you don't need to push this much water through your sump (you will have other means of providing water movement in the tank, yes?).  You can go ahead and use a pump rated at this capacity, but do install a gate-valve on the output side of the pump to allow you to reduce flow if necessary to quiet the overflows/the sound of the water rushing in to the sump>> Are they screened off in any way of just have notches cut into them? <<Just notches...and positioned high enough under the lip of the tank (acrylic) to prevent fish/astrea snails from entering.  If this is a concern, you can try rolling a bit of plastic 'gutter guard' and inserting this in the ell (will need to be checked/cleaned periodically of any accumulation to prevent loss of flow)>> Are they glued in or just pushed on? <<A slip/friction fit>> Would a thread X thread bulkhead work in this case too? <<If you have enough clearance above the bulkhead to 'spin' the elbow, yes>> I'd want to be able to remove the elbow in case it needed cleaning or to be replaced, and would rather have it screw on rather than just push in, for safety's sake. <<The slip fit has not been an problem in my experience, just be sure not to wedge it in so tight you can't get it back out>> The bulkhead screen idea seems good too.  Let me make sure I understand it though. <<Alrighty>> Inside the aquarium would only be the screen, about 3 inches underwater. <<Correct>> On the outside you would simply raise the pipe coming from the bulkhead a few inches up to the point where you want the level in the tank to be, by using a few elbows, right? <<In theory, yes.  I have not tried this myself>> Would it be a big deal that you wouldn't be skimming any water off the surface, rather just below? <<This method doesn't allow for removal of surface film>> Ok, I'll leave you alone now. <<Not a problem my friend>> Thanks again, Jon <<A pleasure to share.  Eric Russell>>

Re2: Overflow Design/Bulkhead Size -- 10/03/06 Eric, <<Hiya Jon!>> Hey, just wanted to say thanks again for all your help. <<Truly my pleasure>> I think you just solved my problem. Jon <<Ahh...is redeeming to hear (read).  Good luck with your venture my friend, EricR>> Bulkheads And Flow - 08/07/05 Dear Eric, I promise this is the last time I'll bother you. <<Hello again Andrew...no bother...really...I'm happy to try to assist.>> But I was thinking about it and thought that (2) 1.5" bulkheads would/could give me around 1000gph. (Please correct me if I'm wrong) <<If you're talking about both draining to the sump, then yes, is quite plausible.  Though I must say, that is an awful lot of water to process through a sump on such a small tank (30g)...the slightest restriction is going to put water on the floor in a hurry.  Not to mention the NOISE it is going to make.  I would recommend using one bulkhead to drain to the sump in conjunction with a smaller pump (say a MAG 5), and use the other bulkhead to feed a closed-loop with another MAG 5 or even a MAG 7.>> I was planning on running a Mag Drive MD9.5.  I calculated that this would give me about 800gph at 4.5' head.  Is that to much to run through a sump? <<Ah, should read ahead <G>...>> I wasn't planning on having a large sump, maybe 10-20 gallons and a separate 10 gallon Plenum.  I was planning on running the return into a manifold and was wondering if I should stick with the 1" bulkheads and run a smaller pump and drill a third 1" bulkhead to run closed loop.  I would only do this if I had no other choice about the sump. <<Now you're talkin'...  Here's my recommendation for the simplest, most manageable configuration in my opinion.  Have three holes drilled for 1" bulkheads...Use two bulkheads to drain to the sump with a MAG 7 return pump.  Use the third bulkhead to feed a closed loop with another MAG 7 pump.  With head loss due to height/plumbing, you'll have a total flow rate of around 600-700 gph I'm guessing.  By using "two" 1" overflows you will be able to increase the pump size a bit (MAG 9.5) if you determine you need/want the extra flow.  Also...if given the choice...go with the 20 gallon tank for your sump...you need to ensure you will have enough "empty space" to handle the drain-down from the display tank in the advent of a power outage.>> It will only contain a skimmer, a little mechanical filtration, and a little chemical.  <<and your pumps>>  Will this be overloaded? <<Assuming you go with the larger of the two sump choices (20g), should be fine.>> Thanks Again (and again and again...) Andrew <<My pleasure my friend, EricR>>

3/4 standpipe on a close loop? 8/24/05 I'm setting up a brand new AGA 75 Bowfront.  It came pre-drilled with a 1 1/4" bulkhead and a 3/4" bulkhead (LFS ordered it that way).  The way my LFS originally told me to set it up was use the 1 1/4 for the standpipe, and the other for the return from my sump.    <Okay> I'm running a Mag 12 in the sump to the return.  It is all working just fine.   However, my X10 controls running the powerheads for my wavemaker burned out in just a few days!  After reading on here, clearly I believe a wavemaker on powerheads is not the right way to go. <Agreed> So I've decided to go with a sea swirl connected to my return line from the sump and set up a couple of maxi jet power heads in the tank in addition. So here is the question: I've thought of getting a bigger return pump and hooking up 2 sea swirls, but I don't think the 1 1/4" has enough flow rate to take advantage of a larger return pump. <Also agreed> Am  I crazy to think of taking my 3/4" bulkhead and using that hole as a 3/4 stockman standpipe (I have space for a stockman but not a Durso design)?    <Won't get you much more... think of the mathematical formula for the surface area of a circle... pi R squared...> The other alternative is to use the 3/4" as a downspout to a separate smaller pump and set up a close loop with an extra Mag 7 I have and leave the flow to the sump alone. <A better idea>   In that case I would connect the smaller pump to a 1/2 sea swirl and the sump return to a 3/4. <Sounds good> Of course the final option would be to drain the main tank and then take male and female brushings and create a 1 inch "bulkhead" which would fit in the pre drilled hole.  However, I worry that this would not be a sound construction. <Me too> (I have looked for larger bulkheads that would fit in the pre-drilled hole, but can't find any, the hole is just too small). <Bingo! Yes> Any thoughts would be greatly appreciated. <Your proposed changes are good... that or re-drilling the tank are your easiest options. Bob Fenner>

Re: 3/4 standpipe on a close loop? Bulkhead f'  8/25/05 Thanks, you all are great!  It is always difficult to guess on these things and I know once I set it up is much harder to change.  One quick update: Decided to do the close loop approach.   By chance I did find a Schedule 80 threaded coupling where the threads fit in the 1.5" pre-drilled hole but because it is schedule 80 the outer lip is larger then the hole, in fact about the same size as the gasket.  I have read of some people using threaded fittings in this manner as the bulkhead. Should I be really worried or is this a safe approach?    <Can be safe... with securing the bulkhead first... with a smear of Silicone... letting set-up for a day or more... and gingerly (so as not to tear the Silicone) threading a fitting over the outside thread...> Of course the sane thing to do would be to just use the 3/4 bulkhead, but I'm just not happy with the idea of such a small overflow.   <Me neither... you would be disappointed I assure you> I still have a few days before I have to make a final decision (wife is tired of the room where it is being constructed is a mess). Thanks again.   <Welcome. Bob Fenner>

Re: Tank flow from Overflow 8/12/05 Quick follow-up.... If I used the 1" and 3/4" holes in the overflow to feed water into the sump and created a new return line should that do the trick (see below) as far as getting water into the sump at a better rate.  Instead of drilling new holes or making the current holes larger. Erik <Might accommodate adequate flow, would still be noisy... Bob Fenner>

Flow question part 2 8/9/05 OK, sounds good.  I will convert all of the bulkhead holes to drains, my question now is what size pipe do I use for the standpipe?  For the 1" bulkhead I used 1.25" PVC for the standpipe, for the 3/4" bulkhead would I make a standpipe from 1" pipe or 1.25" pipe just like I did for the 1" bulkhead? D'Wayne <Any size that is at least the same size as the bulkhead should do.  The only downside to upsizing is that objects (like snails!) could easily fit into the standpipe, but also easily clog the bulkhead.  Extracting them could be difficult.  Since your standpipes should be protected anyway, this is a minor issue.  Best Regards.  AdamC.> Tank flow from Overflow ... not so "reef-ready" tanks 8/11/05 Ok I have read all over your site about micro bubbles and problems of the such, but my problem isn't exactly in that reading and I don't know where else to turn.  I have an Oceanic 75 gal with built in overflow and oceanic overflow kit.  The line to the 38 gal sump is 1" tubing <Too small...> that goes directly into the compartment that contains the skimmer (ASM G1).  There are three baffles, which flow into a refugium and then finally over one last baffle to the return pump (a Mag 9.5) that returns the water through a 3/4" line with a ball valve and then to a T joint to both corners of the tank.  I cannot get a steady flow of water through the line to the sump.  It constantly takes in a lot of water mixed with small air bubbles and at times very large air bubbles. <... yes> I called the LFS and they said I should be getting a steady flow through my overflow to my sump with the setup I have with or without the ball valve. <... no> I have tried to move the standpipe up and down, add a small piece of air line tubing 3/4 the way down to the sump, and play with the ball valve. <... won't work> None of these have worked and I am out of answers.  Is this a common problem or are there any solutions that I am not using. Thanks Erik <Is a very common problem... with most all so-called "reef ready" tanks/kits... the through-puts (holes...) are too small and too few... You need a larger drain line... practically speaking 1 1/2 or two inch inside diameter... two would be better than one... Yes... requiring draining the tank... Please read here: http://www.wetwebmedia.com/overfloboxfaqs.htm and the linked files (till you understand) above. Bob Fenner>

Bulkheads... getting ready to drill, planning plumbing 10/12/05 Hi guys!!!! Like to say it again, great site and info... I am getting ready to drill my 100 gallon tank at the top. I was wondering will 1 2" bulkhead get me by with enough flow for SPS? <Mmm, I encourage you to consider two... maybe 1 1/2" ID... better to have in opposite, upper corners...> I am going to be using a sequence dart. I guess how much gph will I get with a 2" inch bulkhead?  <Depends on subsequent factors... of plumbing, turns, water level over...> Or should I drill for 2 2" bulkheads. <Much better> I just want to get by with one if possible because it makes me nervous drilling the tank. Also will it be fine and the same flow if I just have it flow straight to the bulkhead with a strainer. Or should I put a 90 degree fitting on it with a strainer inside the tank. Thanks and hope this makes sense.  <Mmm, better to use strainers for sure... and a good idea for you to check into using "Tees", aspirating the lines after... for noise reduction, flow... Bob Fenner> 

Overflow  11/9/05 Hello everyone, <Sam in Malaysia> I have a 4'x1'x1' tank that I would like to have 2 x 25mm overflows. I thought this would help with the flow of water since I'm using a 5000L/hr water pump that sucks the water really fast. <Faster than these overflows/intakes will allow> Current residents of the tank are 3 tubeworms, 1 yellow tail damsel, 1 fire goby, 1 pink antennae, 1 button polyps, 1 flower pot, 1 star polyps and Caulerpa macroalgae. I have about 10 kg.s of life rock. Your help is very much appreciated.  Sam Malaysia <... help with what? You likely need more and/or larger intakes... Bob Fenner> 

Overflow from a mini-reef  12/14/05 Hi guys/gals.  I'm setting up a small 16 gallon mini-reef tank to put on my desk and have a question for you.  This is a small bow front tank to which I plan to add overflows. My plan is to drill dual 1/2 inch holes <RMF would make these a minimum of 3/4 inch> (one in each corner) in the back glass and attach PVC "Ls" to each with an enlarged fence atop.  The bottom of the tank is tempered or I would drill there.  My question is this: from your experience, does it matter how deep (distance from the top of the tank to the center of the hole) these holes are drilled? Obviously, one would want to leave room for the pvc L and enlarged fence piece, but for aesthetics, I would like the hole to be as close to the top as possible so you don't see the pipe run the whole depth of the tank.  Or in other words, the pipe would enter from about 4 inches (or so) below the water surface and then make a 90 degree up into the larger diameter fence. Is there any disadvantage to this as opposed to drilling the hole near the bottom of the back wall with a longer section of pipe between the fence and L?  My other tank is a reef ready 100gal so I didn't have these problems. <There is no advantage to having a longer pipe just to bring the water from the surface down to a low-positioned drain hole. You can drill as close to the top as structural/glass integrity will allow and your plumbing/elbows will accommodate.> Thanks for the advice and for all the other help I have gotten from your site throughout the years. <Always a pleasure. -Zo> Peter

About overflows pre-made... this time in an Oceanic product question  - 2/4/2006 Hello folks! <Peter> I just emailed Oceanic to inquire about the capacity of my 74gal bowfront reef ready tank.  I have heard that it is 1200gpm but I assume this is under siphon (which I don't want to do because of noise). <And otherwise ideal conditions... which you/one should not rely on. These 3/4" diameter holes are inadequate... They will change... likely soon... enough lawsuits, complaints>   I'm considering converting the ¾' return hole in the overflow to a second drain hole to increase the capacity. <Good idea... not too close to the existing...> Then I would just plumb the pump return behind the tank and up and over the edge (with a siphon break).  Any reason why this wouldn't work?   <Mmm, nope> Also, to what would you guess the capacity would be increased (would give it a 1' and a ¾' drain). <Would make this 1 1/2"... cutting over the existing...>   Would I need to cut the weir slots larger to accommodate the larger flow? <A good idea... or cut down the height a bit...> Thanks again for all of your help.  Peter <Welcome. Bob Fenner> Re: overflow question  02-05-06 Bob, thanks for the quick response.  One point of clarification...you mention making it 1 1/2" and cutting over the existing hole.  From my understanding, the bottom glass is tempered.  This can't be re-drilled, can it? I've drilled holes in non tempered glass quite a few times... Thanks, Peter <Is an issue... am given to understand that there is technology for cutting through nowadays (have never had success with myself), but if I were doing so here, I would likely abandon the one present hole and drill the larger through the back. Cheers, Bob Fenner> Standpipe/Bulkhead Size  2/18/06 Hello, <Hi Gabe> I asked you guys some questions a couple of days ago but received a puzzling reply that left me without answers. <Sorry, that was my doing.  I could have swore I answered that query.>  I have included the original message and your reply below. I am not sure if this reply means that I should find the answers by searching previously "answered" queries, or that James felt that someone else had already answered this particular query. I am pushed for time on this installation and have already ordered the 2" bulkheads due to space and price.  If you felt as though I did not research this sufficiently I would like to explain myself. I understand my desired flow requires a drain/bulkhead between 2.26" and 2.61" using the calculator at reefcentral.com (which reference I found at WWM.com). I also found that recommendations made by much of the WWM crew on drain/bulkhead sizes seemed to be higher (many times double) than what the calculator provides (I am not sure, but the calculator may provide an "exact" size without any tolerances). <Believe you are correct here.> I also could not find a query on this subject that had desired flow rates as large as mine. Furthermore, there have been some suggestions to increase standpipe sizes to reduce noise levels, but I have not found whether a grossly oversized drain could increase the noise level. I requested your preference or opinion on bulkhead size due to the noise factor and the vagueness of information presented on sizes vs. flow requirements. I did find sufficient information to promote the vent I was asking about by further searching WWM (shame on me). I do hope I have not offended you guys as it is prudent to have such a knowledgeable group on my side. <Two 2" lines should do the trick.  Some people will go with a Durso Standpipe to help eliminate noise.  You can search/read this subject on the WWM.> Thanks, <You're welcome and sorry for the mix up.  James (Salty Dog)> Gabriel Set Up/Sump/Drain Size  - 03/12/2006 Hi....<Hello Mike.> Thanks for your time.  Fantastic web site.  "Before"  doing my homework I bought an all-glass 54 gallon corner tank.  I thought that the 1 1'4" predrilled drain would be enough for this tank draining about 600gph but after reading the fine print I found out that in the corner tanks the flow is only 400gph.  I'm considering using the predrilled 3/4" return hole as another drain and plumbing the return over the top of the tank.  I'm just not sure if the two different sized drains will be a problem and if the skimmer box will be able to handle this additional flow of water without backing up. Any quick thoughts would be appreciated.  <Mike, the 1 1/4 drain is more than enough for a 600 gph flow.  Don't know where the "fine print" came from.  James (Salty Dog)> <<James, after the diameter of the bulkhead is considered, the inside diameter of this through-put will likely be less than an inch... RMF>> Thanks for your time  <You're welcome.> Mike

Re: Set Up/Sump/Drain Size  - 03/12/2006  - 03/13/2006 Are you sure, Bob? Seems like all the bulkhead fittings I've used will allow the entire ID of the pipe to be of use, that is once you slip the PVC pipe in, and look into it, you cannot see any restrictions caused by the bulkhead fitting, that is, the lip on the bulkhead is the same size as the thickness of the pipe.  In using the drain size calculator, for a 600gph flow rate, a minimum pipe diameter would be 1.01 inches.  The results do not specify ID size so I'm assuming it is the actual pipe diameter which is how pipe is measured anyway (I'm sure you know).  A 1 1/4 pipe has a ID of 1 1/4 inches.  If you believe I am wrong...my apologies. James <Am pretty sure the writer is referring to the OD of the hole cut in the tank... the throat of the bulkhead takes up space/diameter. B>

AGA Overflows I have been reading a lot about the shortcomings of the standard overflows that come with certain Aquariums. I have a 90 gallon AGA and was wondering if it makes sense to somehow convert the ¾ inch return line to another drain to increase flow and use a closed loop type of return instead. Thanks, John <Does make sense... either to A) use the current small lines for a closed-loop recirculation system (in place of submersed pump/s, powerheads), B) Re-drill over these holes to much larger... or C) do A and drill new holes... Bob Fenner> 

Bulkhead Recommendations Hello there crew, <Is it, could it be... Aquaman!> I need your help big time. I'm in the process of setting up a 450g aquarium. The plans have already been given to the manufacture 5 days ago. I planned on have 6000gph circulation. The drains consist of (2) 2" bulkheads and the returns are (4) 3/4" bulkheads, <Uhh, not through these fittings> after reading info on wet web media I'm feeling that a need to increase the number of my drain as well as my return bulkheads. Please recommend what size drain and returns I should have and how many. <Mmm, I'd increase both the number and size/diameter of through-puts here... at least two four inch drains, six two inch returns...> The tank will have a center overflow for the drains and the returns are placed on the top of the aquarium towards the rear wall. I will need to quickly call the manufacture to make the adjustment. <Mmm, a bunch more to consider here than you are asking... I wish we had talked over your plumbing/filtration configuration altogether. Please assure me you've read through our (WWM) articles and FAQs files on these subjects... Bob Fenner> 

External over flow, not reading WWM, illiteracy period I <What is the deal with the public and the personal pronoun "I?"... it's capitalized people> was wondering if I could drill some 3/8 or 1/4 inch holes in the back of my glass tank and then build and external over flow. <Too small diameter. Please read here: http://www.wetwebmedia.com/marine/setup/index.htm scroll down to the section on Filtration... read re plumbing, overflows...> I want the over flow to contain the bulk head because I do not want to drill a big hole in the bottom of my tank. also will acrylic bond to glass. Robert Tice <... no. Bob Fenner> 

Water Flow...Not Enough Drains! - 06/09/05 Hello Crew! <<Evening to ya!>> Please allow me to ECHO the many expressions of THANKS from fellow readers for your help, dedication and for the knowledge gleaned from your site. <<Many thanks, is a pleasure to assist.>> I am in the planning stages of a 180 gal saltwater reef tank. PLEASE double check my thinking here. <<Alrighty>> Goals in design: 1). Maintain at least 200 gal of system water AFTER displacement of rock, sand by using a 55gal refuge (drilled 1" drain) on display next to main tank and 55gal sump. <<Would suggest two drains here to allow for ample flow rate through this 'fuge.>> 2) Achieve a turnover rate of at least 30 to 35 times per hour(6000-7000)Super Amp Master at 0 to 5 feet head with 2-2" PVC return and 2- 2" drain outlets. <<Do double check your figures here, I'm thinking you'll need twice the number of 2" drain lines, and even then will be marginal.  Another consideration...this much water rushing through your sump is going to make a heck of a racket.  You may want to consider a closed-loop for the big pump, with something in the 700-900 gph range for the sump return.>> I am considering a through the wall application which would turn a walk in closet into the sump/skimmer/pump room. <<Handy indeed.>> Aside from the risk of divorce it would allow for 0 or very close to 0 head, noise reduction.  Delicate spousal negotiations to follow. <<G>> 3) Turnover rate of refuge 5-10 times per hour (275-550). <<Thus the need for two 1" drains as a minimum.>> Return to refuge with 1" PVC  "T"'ed off one of the 2" PVC returns with check valve to control flow. <<Check valve? No...I hope you mean "gate" valve.>> Refuge drain with 1" PVC to sump. <<Don't over estimate what your drain lines can handle.  Best to "over engineer" here my friend.  I highly recommend you do some reading about this on our site.  Start here ( http://www.wetwebmedia.com/plumbingmarart.htm) and continue with the related links in blue at the top of the pages.>> 4) Dedicate the 2-2" return pumps to overall system FLOW ONLY thus utilizing an additional external pump from the sump (probably 1" PVC) to provide water MOVEMENT in the main tank via a manifold (exact configuration and pump capacity to be decided after experimentation.) <<Yes, the closed-loop manifold is your best bet for the high-flow pump you describe.  Much info about these as well in the links I mentioned.>> (Any suggestions on user friendly Drawing-CAD software?) <<Afraid not.  Try posting your query in the DIY forum on Reef Central ( http://www.reefcentral.com/forums/forumdisplay.php?s=&forumid=3), I'm betting someone over there knows of some.>> Thank You, Benjamin <<Regards, Eric R.>>

Horizontal Overflow - 06/10/05 I'm planning on having a 55 AGA drilled on the top back wall for two or maybe three 1" bulkheads just below the frame.  I want a flow rate of at least 600 GPH and hopefully more like 900gph. <<I would put four drains of this size on this tank.>> <RMF would use 1 1/2" through puts> I want to install a glass or acrylic skimmer box that extends the length of the tank (48") and be approx 1/2 to 2 inches wide and perhaps five or six inches deep.  This will be siliconed to the back wall and the bulkheads will remain inside this zone. <<Go with glass...much better adhesion with the silicone.>> My questions are:  1.)  Am I correct in my assumptions about flow rate from this number and size bulkheads in this application? 2.)  At this level of flow will there be much noise or do I have to install some type of silencer?  i.e. external Durso standpipes?  3.)  Should I install some sort of teeth or mesh to keep out snails etc?  Depending of course on if I need to install elbows on the bulkheads for noise issues.  And finally what type of flow rate will I need from my pump.  I was considering a Mag 9.5 or 12.  I know I can throttle the pump back but will an undersize pump be a better choice?  Like a Mag 7?  Unsure how to proceed and thanks for the help...!  Glenn <<Most folks underestimate what their drains can handle.  Just because a drain is supposedly "rated" for a certain amount of flow doesn't mean it will do so with any margin of safety, and most assuredly it will not do it quietly.  Do some reading here http://www.wetwebmedia.com/overfloboxfaqs.htm and at the associated links in blue.  Much info/help to be found.  Regards, Eric R.>>

Drain Size and Noise - 06/16/05 Hello WWM crew. <<Evening>>   In a response, Anthony stated "1" bulkheads really should only handle about 300 GPH each to be safe and quiet. Thus... to run a 1200GPH pump, you need 4 bulkheads! With your 1.5 inch holes... I'd guess you could only run about 1000PGH through them quietly".  I also read somewhere else on the site that a 1.5" drain can handle ~750 gph. <<I agree with Anthony's estimation.  I originally set up my tank with six 1" return lines and a 1500 gph pressure-rated return pump...still made so much noise you couldn't hear the television or speak in normal tones, even after aspirating the return lines.>> If I drill two 1.5" drains to my sump, will they be enough to handle the ~1500 gph total of my 2 sump return pumps? <<Probably...>> <Mmm, not IMO/E... two 2" lines, vented, maybe. RMF> Would a gate valve placed after each pump be good for "dialing back" if necessary? <<Always a good idea...along with unions to facilitate maintenance.>> For my closed loop system, I was told the size of the drain should match the input side of the pump (1200 gph), which is 1". <Yes>> But a 1" drain handles only 300 GPH quietly.  I'm confused.  Wouldn't it be better to have two 1.5" (or one 1.5" and one 1") drains joining at the closed loop pump to get ~1500 GPH? <<Fluid dynamics can be a funny thing to understand.  The 300 gph recommendation is for GRAVITY overflows/drains.  When the water is forced under power/pressure as when the drain connects directly to the pump the "dynamics" are totally different.  As long as the piping is of the diameter recommended by the pump manufacturer the pump will move the listed amount of water (taking head-height and possible exaggeration on the part of the manufacturer in to account, of course); and any noise, as long as you don't have air being sucked in through plumbing/pin-hole leak, is generally just that of the pump itself.>> Thanks K <<Regards, Eric R.>>

Drain Size and Noise...(Understand?...Soon Grasshopper) - 06/17/05 Ah. Now I understand. How much noise will there be with two 1.5" drains to the sump? <<If you're turning 1500 gph?...the larger diameter will help with air entrainment/flushing, but I think it would still be quite noisy.  You're still processing/dropping a lot of water in to your sump.  My suggestion would be to use just one of those 750 gph pumps for sump return.>> So there shouldn't be any noise associated with my closed loop system if I have a 1" gravity drain (hole at bottom of tank) that leads DIRECTLY to the 1200 gph pump, and little or no need for "dialing back" the return with a gate valve? (Will still have a gate valve on the return just in case) <<Don't think of the return for the closed loop as a gravity drain...it's not...it is the pump "intake" for the closed-loop.  And no, you won't need to dial back the pump.  That's the beauty of the closed-loop...you're pumping "in" exactly what you're pumping "out.">> K <<Do a key-word search of the WWM site for "closed-loop"...lot's more info for your edification.  Regards, Eric R.>>

Tank drilling - size and position concerns Hi guys!  You all are doing a great service to the hobby!  Here comes one more person jumping in...  I have been researching and reading a ton of information here, at ReefCentral, and elsewhere...   <Good> I have recently bought a used 180g 6'x2'x2' tank.  The goal of this tank (my first marine tank) will be FOWLR with the intent of a reef a few years down the road. So I want to set some things up with a reef in mind.  Right now I really only want to address drilling additional holes in the bottom of this tank and the associated overflow.  The tank currently has an end overflow with three 1.75" holes drilled in the bottom.  I am concerned that I will (eventually) need more flow than these holes will allow since I will be limited to three 1" diameter drain pipes and will have to pipe the returns over the side (not my favorite config).  I'm assuming I can get about 1800 gph with three 1" drain pipes. <At the most, yes> I know a company that will drill additional holes in the bottom (not tempered), but I'm concerned about the strength of the 3/4" bottom glass.  Here is a photo of the tank and a CAD drawing of the current and proposed holes: http://home.cfl.rr.com/homebrewed/fish/tank_holes.jpg http://home.cfl.rr.com/homebrewed/fish/tankbottom.jpg <I see> Would you suggest moving the new holes further from the existing? <Yes>   Make the new holes bigger? <Yes> Any other helpful suggestions would be appreciated. <I would make the new holes two inches in diameter and move them midway twixt the wall and existing nearest hole, and slightly further (another inch or so) away from the side... much could be said re glass properties... super-cooled liquids period> The RC calculator tells me I should have 27" length overflow. <?> However, I think I have to go straight across the 24" width if I add holes. <I would stagger the new holes as mentioned> If the overflow turns back to the end wall instead, will I end up with a dead zone that collects debris? <Not with good circulation otherwise, and careful rock, decor placement> The last question is regarding the return line diameter.  If I have a total of five 1" pipes through the bottom, I think I could do four drains and one return.  I want to take the return water up to the rim of the tank, split it along each 6' side with a few outlets along each side.  Would a single 1" return pipe be sufficient to handle the return water for the whole system (4 drains x 600 gph = about 2400 gph)? <Mmm, better to use two or all three of the existing lines here... devise a return manifold for front, back with the two outer ones...> Would I be better off just using the three holes as-is with two as drains and one as return, then adding some Tunze pumps for additional flow? <Mmm, no... insufficient diameter... a noisy mess now and frustrating, potential trouble...> The last question - is there any way to get a larger diameter pipe safely through that 1.75" hole?  I'd love to be able to use a 1.25" pipe with the 1.75" holes, but my understanding is that I can't do it. <Can "cheat" and use thinner through-hull fittings, smaller schedule plumbing (like 200 PVC... as in rated for 200 PSI... instead of 40... for 400...), but don't do this... Much better to have new holes made. Bob Fenner> Thanks, Randy

- Overflow and Plumbing Flow Rates - How much over flow (max) do you feel a 1.5 inch overflow can handle, per hour? <Well... please keep in mind that these are two separate questions. A 1.5" piece of tubing can flow roughly 3,500 GPH. The "overflow" may [in fact probably will] limit this by the size and number of slots that allow water to pass through it.> Now, how much do you feel it should handle, being conservative and safe? <Again, depends on the manufacturer of the overflow.> Same questions for a 3/4 inch overflow (for a 90 gallon oceanic, drilled with a 1.5 and 3/4, I was contemplating using both for overflow, but at a rate well below what each could handle collectively). <Not entirely sure. Know that Oceanic/AllGlass have improved their overflow boxes to handle higher flow rates, but you should really get in touch with them to see if their overflow box will in fact handle what you're looking to push through it.> hear that 1.5 inch can max out at 750 GPH, maybe I'm wrong. <Do believe it's more that that. The old style AllGlass overflows could handle 900 GPH per overflow box, the Oceanic ones could handle about 1200 GPH> Not sure of the safe/reasonable level. <Again, should contact the manufacturer.> I haven't seen info. on a 3/4 as it relates to "overflow". Thanks very much. <Cheers, J -- >

Overflow Box 7/9/05 Dear WWM Crew, <Glenn> I'm looking into building a custom over flow box and have questions on what its dimensions should be to handle the water flowing through it. A year and a half ago, I decided to add sump/refugium for my 75 gallon aquarium. I decided to use the skim box that came with my Remora Pro (The one for the Mag 3 pump) as the overflow. I used silicone to seal off the pump side and return sides. I had my tank drilled in the back about 2 - 3 inches from the top and 2 - 3 inches from the left side (looking front). The bulkhead runs through the tank into the box, which is held in place by silicon and the bulkhead. I estimate that this drain runs 350 - 375 GPH through the sump / refugium. The Skimmer's Mag 3 pump sits in the return side( I had to cut out the outside panel of the return side to fit the pump in there. <Innovative> Now I would like to replace this box, with a box that will hold both the overflow drain and skimmer pump. The reason are for skimmer efficiency and appearance. I recently read a Reef Central thread from Anthony explaining how to help your skimmer collect more skimmate. For HOB skimmers he said to move the pump as close the surface as possible. <Yes... more of the phobic molecules there that you want to remove> This one came with a skim box and I simply want to get that back. I don't want to tear the tank down again (Cause I have a DSB), so my plan is to drain the tank to a few inches below the drain. Remove the old box and bulkhead and add a new custom box that will house both the drain and skimmer pump. My question is how to figure out how much collection surface area this box will need and volume to keep up with the 350 GPH drain and up to a Mag 5 pump( In case I decide to upgrade.) So it would need to continually intake 700 - 1000 GPH without ever running dry. The current box is (L x W x H): 10.34" x 8" x 4.25"). Of course only about 2/3 of that is used by the over flow. Thanks. Sincerely, Glenn Serpas <Mmm, "bigger is better" is about the simplest, best statement that can be made... Please see WWM re relative sizes of bulkheads, other considerations for allowing this much flow... and safety measures should it get blocked, water level drop... Bob Fenner> Overflow size related to bulkhead flow 8/2/05 Hi Guys, I love this site! I have learned SO much over the past 2 months from reading all these FAQs, actually, the more I read the more I stall in the setup of this tank- I want to get it all perfect. <There comes a time...> I am still in the planning stage of my 'dream' reef tank. So Far, I have the following: 225gallon (72x24x30)acrylic tank, 48X20X20 acrylic Sump, Euro Reef CS 12-2, Sequence Barracuda pump. <How nice> I am fortunate to have a small bathroom on the other side of the wall where my tank will be. This will be a dedicated room for extra gear: the 1/2 hp chiller, the RO/Di, a salt water holding tank for water changes, and now my latest idea- a large refugium with a DSB, some live rock and plants and lighting.   <Great> I plan on having 1/2 inch of substrate (for looks) in the main tank, mostly because I prefer to save the 6" in space on the bottom of the display tank. Ok, I had the builder upgrade the plumbing, so the tank now has two 1.5" (id) drain bulkheads and two 1" returns through the bottom of a 20"x5" overflow in the center back wall of the tank. The returns are set up to have PVC pipes coming up through the overflow then up and over into the tank. Now after reading more, I have decided I want even more water flow than the two 1.5" drains, and possibly, two separate pumps- one for the sump (where I will have the skimmer and lots of LR, and another for the refugium. So here is my plan: I am thinking of using all four holes at the bottom of the overflow as drains. I was thinking of plumbing the two 1.5" drains plus one of the 1" bulkhead to go the sump, returned to the tank by the Barracuda pump via a manifold (with many adjustable outputs) lining the upper rim of the tank. Now the other 1" bulkhead I was thinking of plumbing it to drain to the room behind into a 65-85gallon refugium, then pumped back to the main tank via another external pump using another manifold that would go down along the side of the overflow, across the bottom of the o.f. and back up the other side of the o.f. to complete the loop. This 2nd manifold would have outputs directing water flow behind and through the LR, along the back wall and along the bottom. What do you think? Overkill? Would you do it in another way? <Sounds like a very nice change, upgrade> Does this sound like it can work? When upgrading my plumbing, the builder of the tank (who thought 1" drains and 3/4 inch returns was plenty of flow-ha!) said that the overflow needed to be made larger as well in order accommodate the extra flow of the 1.5" drains. This is why it is now 20"x5" Can I use the other two 1" bulkheads as drains? <Sure> Will this overflow provide enough flow for all four drains like I would like to do? <Yes, likely so> If not can I modify this overflow by drilling a few holes in it toward the top to let more water flow in to the drains? <Can be done... use a sharp bit, tape over the area/s to be drilled, use a variable speed drill... go slow, low pressure...> Will the overflow/water draining in be more noisy with these 4 drains? <About the same> Thank you so much for your help, you guys are doing an amazing job. I would be lost without your help (the LFS here in AZ is clueless, <Actually, there are some great shops in the area... are you familiar with Aqua Touch? and Kingsley's out there?> they never even heard of Euro Reef skimmers or Sequence pumps) Regards, Nic <Ah, wherever the info., inspiration come/s from... Bob Fenner> Flow question 8/4/05 I have a 180 gallon reef ready Oceanic tank with two overflows, each has a 1" and 3/4" bulkhead.  I built a Durso standpipe to use in each overflow attached to the 1" bulkheads and each of the 3/4" bulkheads is fed by a mag drive 1200 pump.  This has been up and running with no problem (no fish yet, still cycling) but when I told someone at the local fish store he said the flow from the mag pumps is too much and that the drains couldn't handle it.  Well, it is handling it but I wondering if this is a disaster waiting to happen.  If so beings I already have the pumps I would like to stick with them and perhaps convert the 3/4" bulkheads to drains as well.  What are your thoughts? <Since the "Dursos" essentially act as siphons, <<Mmm, no. RMF>> they can handle much more flow than a standard drain.  The problem is that any small obstruction (snail, algae, etc.) could back the drain up enough to cause a flood.  If this was my tank, I would use all of the available  holes as drains and plumb the returns over the back edge of the tank.  Another option is to maintain a water level in the sump that is low enough that the pumps would run dry before the tank overflows, but this is often impractical.> BTW the pumps sit directly below the tank, one pump has about a 6' vertical rise while the other has a 6' vertical and 5' horizontal run.  I'm not sure how much head pressure that creates and maybe makes the flow acceptable for my drains (i.e. I'm not sure what the flow rate is for the mag drives with the amount of head pressure).  D'Wayne  <I am pretty sure that Mag-Drives are rated at 4' of head, so you probably are achieving close to the rated flow.  Best Regards.  AdamC.> <<These tanks/lines are decidedly NOT "reef ready"... too few, small diameter... I would have re-drilled or added to. RMF>>

Complicated calculations of water flow 8/4/05 Even after reading hundreds of FAQs about plumbing I am still trying to figure out the step by step process of flow calculation. <Mmm, there are works (printed) re such subjects> My goal: 3000-3500 gph system flow, 220 gallon main tank, 20x5" overflow with two 1.5 inch bulkheads and two 1" bulkheads (considering using all of them as drains) I decided to go to a larger sump to handle this flow rate and minimize micro-bubbles so it will be 55x25x25 which will give me at least 100gallons of usable volume <... and not running all this flow through it...> Calculating head pressure at RC got me nowhere because I intend on installing a large (many t's) output flow manifold, as well as 2 lines for 2 sea-swirls, further complicating the calculations are T offs from the output of the pump for the chiller, and the large refugium. Also the many uses of 90degree elbows since all the equipment will be in another room behind the main tank, and the changes of pipe diameter going to the manifolds, chiller...etc... <Yes, gets involved> I am upgrading to a Sequence Hammerhead which does 3600gph at 15feet of head pressure. I am guessing this will be more than enough power...the top of my tank is 6feet high, pump is on the floor... <Yes, sounds about what you're looking for> After talking with Rich Durso, he mentioned two 1.5" bulkheads (with a proper overflow) should be capable of 3000gph or more, <I would rather have two, even three two inch lines...> I am thinking of using all four (the two 1' bulkheads also) because of restricting issues such as 90degree elbows, running the plumbing back 12 ft of so, and the use of micron bags...etc... <Pi R squared... what's the relationship twixt the one and one and a half inch lines in terms of surface area? Surprising, eh?> He stressed that having 4 bulkheads with Durso standpipes will be very tricky to manipulate the air intake (because one would not know which pipe to adjust... <What?> meaning lots of trial and error...)and may lead to 'the flushing effect' <With this much flow through these four proposed lines... undoubtedly>   He further recommended I try going with just the two 1.5" inch drains first then if I need more flow to add the other two 1 inch drains. But how can I calculate what is really happening as far as flow? <See the references cited on WWM re> I have seen people mention calculating out coming water out of the pipes by timing flow into a measured container. Is this done by filling the overflow and letting it drain through the bulks naturally, measuring the water at the end of the plumbing before it goes into the sump? <This is one approach, yes> This would be just the gravity part of the flow, right? <Yes...> The pump's draw would increase the flow drastically by sucking the water through, <Uhh, no> but how do you measure this once the sump is full and running with the pump on? <Can only be approximated... but there are other means... flow gauges, dilution of dyes and use of colorimetry...> Lets say I go with the 4 drains, the manifold, sea swirls, and everything else, with a valve on the output side of the pump just in case too much flow... <Good idea> bubbles...etc... After it is set up, how can I find out my net GPH flowing in the system? <For you, perhaps a simple corrosion-proof flow gauge is best> This is a mystery to me, perhaps you can shed some light on it for me. Will it be a nightmare for me to go with the 4 drains and try to get them all to work properly and quietly with Durso-standpipes? <... the number, size is of no consequence in terms of "adjustment... they are independent of each other...> Is there a better method I should consider for draining these bulkheads quietly/efficiently? <... yes... posted on WWM...> Your help is very much appreciated! Also, thank you to Bob F. for recommending the LFS:  Aqua Touch, here in AZ. This will be a huge help! :) <They are fine fellows, very good practices... knowledgeable. I would see them... in person... re your plumbing design... I would figure out how to add more surface area to your drainage here... at least two two inch inside diameter through put... may require capping, re-drilling... If/when in doubt, read here: http://www.wetwebmedia.com/plumbingmarart.htm and the many linked files above... you will understand, through study, what your options are. Bob Fenner> Keep up the good work, Nic

Tank Sump Flow Balance Problem <?> 8/5/05 We're having a flow balance problem we need help with.  Setup is basically a 125GL acrylic display tank with a 60GL sump/refugium, plumbed with two CPR CS10 (1400 GPH) overflows on a 1-1/2" line to the sump (ball valve in line to control flow to the sump), <No need....> and a Supreme MD36 Mag Drive Pump (3600 GPH @0'head) return, split into three 1" return zones, off of a 1-1/2" PVC manifold. Zone 1) 3/4" manifold to five LocLine valves around the top of the tank, controlled by a 1" valve, Zone 2) 3/4" manifold to two LocLine valves at each end of the tank, bottom and back, and to a SCWD, center of the tank, on a 1" valve Zone 3) a 1" bypass/return from the sump pump, back to the sump (to balance flow) on a 1" valve. The sump is divided into three areas, first, 7" wide, holds a Turboflotor 1000 Multi skimmer, three baffles (over, under, over), an open area for a future refugium, baffle, and 6" pump area. <Okay> Now, a balanced flow between the tank and the sump can only be reached by shutting off the zone 3 bypass valve, and low tank zone 2 valve, and closing the upper tank zone 1 valve to one quarter open. The flow from the upper zone 1 (five outlets) is only moderate (not even as much as a power head).  It seems that the flow from the CPR boxes (straight drop, one 90 elbow, no restrictions) is way too low for the pump's capacity (Approximately 4' head, and the two zone lines are 5', 1" vinyl flex lines into 3/4" manifold lines). <Yes> The pumps documentation calls for a minimum 1-1/2" input and output lines, on 1" threaded fittings.)  I expected noise from the pump, but it's WAY too loud for a living area. <Time to trade this pump in for something smaller, more quiet... or...> We have fan and round nozzles for the LocLine valves, not yet installed, and I understand that, with a nozzle restriction that even though flow will not increase, <It will decrease> water velocity should.  The other option we're considering is restricting the 3/4" lines at the output to 1/2", and switching to 1/2" LocLine valves.  The idea behind valves with nozzles at each of the outlets is to be able to control and direct flow in the display tank. The overflows seem to be working correctly, what suggestions would you have for the return situation (pump, flow, noise) ? <... trade this pump in... or add overflow capacity... these are your two options. Bob Fenner>

Aquarium cover and overflow size I am building a 90g partial wood tank and was wondering if I should put a piece of plastic or glass over the top opening even though I am putting a 6" canopy on it just not sure what to do here. And any help would be appreciated.  <a glass canopy may still be necessary if for example you are using metal halide lamps that need UV filtering and protected from splash> Oh one more thing I put in a overflow box for my trickle filter and was planning on using 11/4" bulk head fitting will this be enough for say a flow of 600gph or so I'm sure it will but any thoughts. Thanks, Eric <that will be close or not big enough if you actually get 600pgh to the top of the tank. If you are only getting something closer to 400gph to the tank because the pump max is 600 against the head pressure on return from the sump, you may be just fine. Anthony>

Iwaki and overflow Thanks Anthony for your continuing help. <very welcome, indeed> Is my overflow the problem or is it the diameter of the bulk head?  <depends on what we are calling an overflow drilled bulkheads through a tank wall, internal bow, external box, etc. Bottom line really is how big/how many lines feed the sump from "whatever" above> It has about 23 1/4 inch wide 3/4 inch tall slots cut into the overflow. I can easily cut through some of the holes on my overflow to increase water drainage if needed.  <this will not change the reality of the drain line behind it... if it is a one inch line, then it can only handle so much from upstream> The internal diameter of the bulk head drain is about one inch. How much water drainage can a 1" export hole handle?  <realistically 300 gph per one inch line, but at a noisy siphon, toward 500 gph> The Japanese Iwaki MD-30RXLT is rated at 960gph at 4' and given the prior information, would I be pushing the limit with my Oceanic Reef Ready tank if I modify it a little. Could I use a pump with this much flow?  <in what sense? Does a reef need it... absolutely and then some, or... does a fish tank need it, probably not> I simply cannot believe Oceanic would make such a lame reef tank.  <believe it... it is very common among manufacturers in general... extra overflows drive the price higher and bump them away from price conscious beginners (the staple of the market: newbies)> I do not know if the information I got from Oceanic is to be believed. Seems like it should handle it well but I can not afford to be wrong. <nope, I believe it... most tanks have weak overflows and are forced to use powerheads. Do look into Gemini top-mounted pumps (Aquarium Products distributes them.. a less expensive version of the German Tunze Turbelles... all great pumps but very expensive> Zimmy <regards, Anthony>

Overflow Box for a 180 gal All Glass tank Anthony, I need to find an overflow box for a new 180 gal ALL glass tank . The overflow box will be in center of back of the tank with two 1-1/2 inch bulkheads  off set hear the top to handle the water return to the sump, It will handle 5000 gal per hour. That should make it reef ready?  RGibson <Hmmm... this is very subjective here, bud. But relative to the complaints of many aquarists that find some of the so-called "Reef Ready" commercial tank overflows inferior... I would be content to have a 180 gallon overflow that could quietly handle 2000 gallons. This is reasonable in my opinion. The hard coral reefers will tell you that even this is inadequate. A 180 gallon SPS tank will have over 3000 gph of circulation or it will fail within 2 years due to complication in part from the inferior flow dynamic. I'll commit to that! So... what is enough? I understand the mfg's need to keep price low... and this my contentment at 2000gph for "reef ready" which will keep most common and hardy soft corals well. Best regards, Anthony>

- Flow Dynamics - <Hi, Bill, JasonC again...> Hi guys a couple things that don't make sense to me in your return E-mail to me. I asked you how many overflow pipes you thought I would need to get around 4000 GPH from the overflow box to the sump your statement was <<How about this: for schedule 40 PVC 1.5" will give you 60 GPM, 2" will give you 150 GPM - you might want to consider 2" or larger for this application.>> What I don't get is you say a 2" will give me 150 GPM and a1.5" will give me 60 GPM. So that is saying that one 2"(150 GPM) will give me more than two 1.5" (60 GPM + 60 GPM = 120 GPM) What I'm thinking if I had 2-1.5" pipes that would be like having one 3" pipe. <It's really true - without digressing into a long discussion of physics and geometry, it has to do with induced drag and the actual area of the inside of that pipe... but it is in fact true - one 2" pipe can flow more water that two 1.5" pipes.> Something is not adding up right here. Could you explain to me how I will get more flow out of one 2" then I would get out of two 1.5"? <Not in this email - if you are really dying to know the answer, pick up the book Aquatic Systems Engineering by Pedro Ramon Escobar - the answers are all there.><<The surface area of a circle... pi R squared... do the math... 2" is more than twice the surface area than twice times 1.5"... RMF>> Also how did you derive at these numbers now this is siphon only no pressure (2"=150GPM &1.5" 60GPM) is there a formula or a chart (on siphon flow) that you got these numbers from?. <Those numbers reflect maximum flow, most likely under pressure which is going to be about as much as you can push through there. Again, pick up that book - it has all the math and related formulae in there.> You also state that I should go with a 2" or larger a 2"@150 GPM = 9000 GPH  I only need 4000 GPH. <More is better for this application. And really, the tank isn't going to overflow more than you are pumping in, with multiple 2" pipes you are just creating a margin for error.> Would I be better off going with a 1.5" and a 3/4" (1.5"@60GPM & 3/4" I'm guessing about 30 GPM=90 GPM=5400 GPH. <No, it doesn't make any sense to try and size things exactly - no room for mistakes.> Man ya need to be a rocket scientist to figure this out! <Not exactly.> You also stated(>In fact, the volume of your tank is large enough that overflow boxes would be unwise.>) (WHY did you make this statement?) Isn't there thousands of people out there using overflow boxes. <On tanks much smaller, yes... and they still have large problems, which means with 650 gallons, your problems can/will be even larger.> I'm sure they all can't be having these problems with siphon tubes getting air in the tube and causing a disaster. Or am I just going about it the wrong way?<I think so, but this is my "opinion" - you're not obliged to listen to my advice at all.> The glass is bullet proof glass I was told I would be taking a big chance in drilling it some even told me it can't be drilled. If you think it is too risky for me to run a overflow box with a sump (believe me I don't want any floods she'll have me sleeping in the shed) <Oh, no doubt... as well as a potential insurance cancellation - no thanks.> I really want to get rid of this pain in the *** canister filter and fluidized bed filters. I'm also unable to use a Protein skimmer because the top of tank is to high off the floor 65" this is where a sump would come in handy. Do you know any other way I can make a better filtration system on this tank seeing you think my idea of a overflow box and sump is to risky? <Again, I would query around with knowledgeable glass people - many tanks of this size are drilled, and there is a good chance your glass is drillable too... probably not with the run-of-the-mill glass cutting kit, but it can be done. It will probably take a day or more, and you'll probably have to drain the tank, and house everyone elsewhere temporarily.> I hate to keep bugging ya about this but I sure could use your help. <No worries.>     Thanks again guys.  Bill <Cheers, J -- >

- More on the Dynamics of Overflow Boxes - Jason Bill here again <Hi.> I promise I won't bug you again on this overflow deal could you please go to this site (http://atlas.csd.net/~cgadd/aqua/overflow.htm according to the plans on this overflow box if built and installed it correct way you should never have any problems with air getting in the overflow tubes or creating a siphon brake. Could you please take a look and let me know what you think. <Well, personally, I try not to use the word "never" - it's very final, and quite all inclusive. Will the person who designed this overflow buy you new carpet should the design that 'never fails', fail? All overflow boxes have a similar problem: the siphon tube. Likewise, it's not that overflow boxes don't work at all, but rather that they are prone to failure, and because Murphy's law will always reign supreme, it will happen when you aren't home. Personally, I don't trust overflow boxes of any type. If you are set on this solution, install double the number you think you might need as a redundancy measure so that if one or more fail, you'd still have some others to keep you from sleeping in the shed, and also keep the insurance wolves from your door.> I do very much value your opinion. Thanks Bill <Cheers, J -- >

- Plumbing the Overflow in a Small Tank - To the experts, Please help I'm going nuts! I have searched the web site for hours and cannot resolve my plumbing problem. These are the basics. 30 gallon tank with a 10 gallon sump. DIY overflow (2 Lee's breeder boxes) 3/4 U pipe and 3/4 bulkhead fitting. 3/4 tubing down to sump. Return back to the tank is as follows: Mag 5 pump to 1/2 in. tubing to a Y fitting to 1/2 in. tubing to 1/2 in. 90's with Line lock fittings ending in the main tank. Now to the problem. I can't run the Mag 5 full open unless I remove the Durso stand pipe I've installed in the over flow. I have made 3 designs with the same results. All are design's from Mr. Durso's web site. All are based on 1 pipe size larger than the bulkhead, meaning they are constructed out of 1 in. pipe tee's, 90's etc. . I even made the straight 1 with out the Tee. All with the same results. Also can you help me out with flow rates with a 3/4 bulkhead and a 1in. bulkhead in my situation? <Hmm... think you are suffering from a couple of issues - first, I'm pretty sure the outlet of that pump is 1/2" which means that you are not restricting the pump when you use 1/2" plumbing which in turn means that the pump will perform at the rated flow. So onto the bulkhead - I think the maximum flow rate for a 3/4" bulkhead is 1,000 GPH, but not sure what the standpipe would do to change that - you might want to experiment by taking off the top of the Durso, so you just have a straight pipe, see how that runs with the pump wide open and then add the parts one by one until you find the limiting factor.> All help would be greatly appreciated, Thanks from a big fan. <Cheers, J -- ><<The flow rate of this pump is too great for this system/drain pipe diameter to accommodate. RMF>>

Pump Size and Overflows Dear Bob and Crew, <Scott F. your Crew member today> How do you guys rate the Mag Drive pumps in  terms of reliability? <I find the new Mag Drive pumps to be quite reliable> I was thinking of getting the MD24 for a 75 gallon with 55 gallon sump. I was hoping 4, 1" bulkheads could handle 1900 gph. Do you think I'll be ok? <I think that they will, but with little margin. You may want to go for 1.5" overflows to be safe. Regards, Scott F>

-Who's rating these overflow boxes?!- Hi Guys! This is the first time I'm writing (most of my questions have been answered by searching and reading the FAQ's). <As most should! A big pat on the back for excellent self research! We're glad you've found it useful.> I want to say first, thank you for the awesome site.  It has helped me out enormously!  My question has to do with an overflow box that I purchased a while back.  Basically the overflow box contains a prefilter box that sits in the display, two J-tubes that siphon the water out of the prefilter box and a holding container in the back with two 1" bulkheads for draining.  It supposedly does 1200 gal/hr. <1" U/J tubes can handle around 600 each, so that sounds good.> In a nut shell my circulation goes like this:  Water siphons out of my display via my overflow box which then is transported to my sump via two 1" flex tubes that dump the water into the first compartment of my sump.  A Mag7 pump (external) pulls water out of the first compartment and pushes it into the ETSS Reef Devil Deluxe skimmer (external) which empties the newly skimmed water back into the first compartment.  The water goes under the first baffle and over the second to enter the refugium (sump dimensions are 24W X 18D X 16H, the refugium is 15W X 18D X 16H).  It then overflows into the last compartment where it is sucked up by the Little Giant 3MDQX-SC and is transported through 1" PVC piping and a 1' black tube back into the display having to first pass through a ball valve, check valve, and two 90 degree bends. The Little Giant pump sits about 4 ft. from the top of the tank. With two 90 degree bends, all the valves and tubing, plus the 4 ft. of head pressure my pump is pumping at most 875 gal/hr (rated 1,000 gal/hr @ 3 ft. head)!  And that's looking at it from an optimistic view point.  Currently, if I don't close the ball valve on the return about an 1/8 of a turn the pump will pull all the water out of the third compartment faster than the overflow can put the water there! <Hmmm...> I'm wondering did I purchase a junk overflow box (it is a non-named brand, purchased from a plastics company) or is it my setup that is slowing the water down too much? <The overflow box should be fine as long as the u-tubes are the standard 1" diameter ones.> Should I purchase an overflow box with a little more capacity to keep up with my pump?  Everything works right now but I'd like to use the full potential of my pump.   If there are any suggestions you could give me I'd really appreciate it. <Suggestions: Assure that there are no kinks or needless 90's in the tubing running from the overflow box to the sump. Make sure nothing is blocking the 1" drains in the overflow like clogged sponges. Check to make sure that the problem isn't simply a case of not enough water in the sump by opening the valve on the pump, and adding more saltwater to keep the chamber full. You'll want to stop this madness if the tank looks like it will overflow and take all that water back out. Heck, if it doesn't work you've just done somewhat of a water change! Basically, there's no reason that you can't run your pump full throttle on this setup. If the water is draining unrestricted, then maybe the u-tubes are too small or clogged. Try a few more things before giving up on your overflow. I hope this helps, I'm sorry I don't have a straight answer for ya! -Kevin>Right now I'm looking into getting a new overflow box from a different and notable company that is rated at 1400 gal/hr but wanted to know if it will even help.  Thank you very much for your time. Chris

- Need Some Opinions - Hello Bob.  <Hi, JasonC here in his stead.>  I'm in the process of setting up my acrylic 48"x13"20" reef tank that's been down for a few years due to moving and busy schedule. Am redoing the stand and hood too. Our living room looks like a workshop :) Would like someone to hold my hand as I venture forth with some plumbing advice/preferences. Technology has advanced a bit while my tank sat. The aquarium has one 5"x5"x19" corner overflow with a 1" bulkhead in the bottom, returning to the almost finished sump/refugium I am now making. My intention is to: 1) Drill another overflow in the opposite corner matching the existing one making two 1" bulkheads (large enough or drill them out to 1 1/2"?) using Durso stand pipe technology.  <Two one inch drains on this tank will be fine.>  I noticed on the Durso web sight that the stand pipe seems to only come in 1". Is there a reason?  <Yes... is the most common hole size drilled in glass tanks for the drain. Can easily build a 1.5" Durso-style stand pipe... have a self-made one in my tank.>  Will have 3/4" to 1" (preference?) return lines come up through same 5x5 boxes.  <One inch would be best... will give you better opportunities to upgrade the pumps, plumbing.>  Perhaps employ a squid valve to these return lines and a sea swirl (if needed) in the middle of tank on a separate pump.  <Sure.>  Am worried about water velocity hurting critters using a squid that will isolate return pump to only one line at a time. Valid concern?  <Nah... these have proven to be very good as water flow devices and in fact the switching back and forth is much better than a single point source that doesn't move.>  Was thinking of a pump that does around 1000gph. Good #? Pump recommendations?  <I'm partial to the Iwaki pumps, but there are many others that will work just fine. If you go for the bottom of the price scale, do yourself a favor and buy two, for redundancy's sake.> 2) Make a new, longer, center back overflow wall, say 16"x4", for improved surface skimming and looks. If I go with this option, I will either drill two bulkheads in the bottom and utilize the Durso stand pipe arrangement, (how big) or come in from the back of the tank up by the water line with two 2" bulkheads.  <If on the back, two 1.5" bulkheads would be fine - if in the corners, then 1" would be fine as well.>  The return lines have the same options, up through the bottom or in from the back.  <This is a call for you to make - it's your aesthetic that you need to please. No functional difference between the two.>  My worry with having bulkheads up high without stand pipes is noise. 2"ers should be plenty for 1000gph though, true?  <Two one-inchers would be fine for 1000 GPH. You are likely correct that any size vertical bulkhead used as a drain will be a little noisy.> Just bouncing these ideas around in my head, trying to think of all the + and - .  <No worries.>  Would appreciate any feedback you have on what might work best.  <Think you're on the right track.> PS: Am thinking of getting a new skimmer. The Aqua C caught my eye. Is it worth the $?  <Is what I own... think they are well worth the money.>  Also thoughts on a calcium reactor? Never had one.  <If you're planning on clams and/or stony corals, then this is a must. Otherwise, a good accessory to have but not a "must have" - am partial to the Knop reactors.> Thanks for the help, One who has definitely got the bug going again, (just ask my wife) Jim <Good stuff. Cheers, J -- > 

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