New tank isn't drilled (but overflow required!)
Hello Bob, would like to know which overflow would be ok / compatible with the jewel Trigon 350ltr,and return pump required (Eheim 1260/ ocean runner 3500 or what do you advise!
<I am much more "positive" re the use of such add-on overflow "boxes" than many of my cohorts here at WWM... for a system this size, for safety's sake, I would utilize two such devices... either tying in their discharges to your sump with a tee or allowing each to overflow separately>
   Sump size is going to be roughly 27x15x18 with live rock, Caulerpa and then return probably housing carbon/ heater. Rowaphos I would  put under direct flow from overflow in a basket or something.
Would you suggest any material different from above in relation to  sump, your expert advice would be greatly appreciated
  Thank you ,I Smith,
Preston, Lancs, UK.
<All sounds about right. Bob Fenner>

-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

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>

Siphon box prefilter 1/15/03
Hi Crew!  Easy question today. As I do not have a drilled tank, I am forced to use a  hang on siphon box. I seem to remember reading that the foam filter should  not be used as it will go biologic (sp?) and then become  a source of  nitrite/nitrates in the sump. Is this correct? If so , should the foam filter  be used? or just go without? My sump is really just a refuge with live rock rubble for growing critters. Thanks as always.
<Some nitrate will be produced in the sponge filter, but I doubt it would be enough to be of concern.  Unless you need to protect the drain from snails or other animals/objects entering and clogging it, there is no good reason to have it.  Bottom line... I would base the decision on flood risk, not nitrates.  HTH.  Adam>

Re: siphon box prefilter 1/16/03
Adam,  I'm sorry to bother you again but I did not post my last question very well.  I am so stressed out about this, that I can't write clearly. Maybe I need a  hobby? I know! I'll get a aquarium!
<No bother at all!  And by the way...  I tried that I need a hobby, how about an aquarium thing with my wife and she didn't buy it for a second!>
With the overflow drain pipe going into the sump, should it be above the water level in the sump or should it be below?? Thanks
<Sorry for passing over this part of your question.  IMO it really doesn't matter.  I prefer to put under water because I found it to be quieter and makes less salt creep.  HTH.  Adam>

Re: siphon box prefilter// follow-up 1/15/04
Adam,  Thanks for the fast reply. I was referring to the big round filter in the drain box on the back of the tank, not the skimmer box with "teeth" on the inside. Would you still not use the cylinder shape foam filter?
<Hmmm...  I am pretty sure that is what I was thinking.  Snails can be quite feisty and climb over into the "outside" box of an overflow assembly.>
I also have a question on the drain line going into the sump/fuge. It is a 1" PVC pipe going straight down. I have checked the FAQ and some say the pipe  should be above the water line, some say it's OK for it to be below? I am  trying to make it as quiet as I can, but it still makes a loud flushing noise. Is this just the "nature" of these boxes? Are they all noisy? Thanks again!
<There are a couple of ways to quiet this down.  One is to build a "Durso" stand pipe in the outside box of your overflow.  If you do a search on the internet for "Durso stand pipe" you should find a diagram.  You can also cover the top of the overflow box to muffle the sound.  Best regards, Adam>

- 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>>

Overflow Question
Hey! How is everybody? <Beautiful day in San Francisco.  Ryan Bowen with you today> Thanks again for such a great site! Got a question.  I have an established 40 gallon tall and I want to add a sump but it just isn't possible for me drill holes for an overflow. <Hmm...Most overflows require no drilling at all>  I'm not sure how to get the water movement correct. <Choose an overflow with about a 400gph rate.  Since you're not going the drilling route, you will need a submersible pump, and don't skimp.  The cheaper ones add a lot of heat to the water.> I have a ten gallon laying around that I was planning on using for the sump. <Go to PetCo, get a super-cheap 20-30 gallon instead.  The extra water volume is the true reason for all this labor- 10 gallons is barely worth the effort.> I was thinking about using 2 of the same pumps (quiet ones, 300gph) to move the water to the sump and back up, into a SCWD wave maker, then into the display tank. <Hmm...I would use a CPR Overflow or a Tunze outlet.  Look up some DIY Sump designs here: http://ozreef.org/ And then pump it back up with an adequate pump.> I don't about all the water pressure, gravity, calculations and stuff. <Trial and error can be pricey, so you may want to read the Circulation FAQs> The top of the tank is about 4ft off the ground.  What can I do to make this work without drilling? <See above> My main focus it get everything I can out of the display and off the back of the tank. <Great> The health of the tank is good and I think a sump could make it much better. <Can't improve perfect health!> I cant afford a bigger tank and I want my 40. Any advice would very much appreciated.  <Surely!  Good luck, Ryan>
-nick

U-tubes 2/5/04
Hi, from Barry in warm Canada (-45 deg Celsius). My first time on WWM.
<greetings my friend... and welcome>
I would appreciate your opinion on u-tubes. I work as a doctor in Canada, but grew up in South Africa where I kept marines in my youth. I wanted a INTERNAL drain that would suck off the bottom close to the sand. I felt this would suck up the larger pieces of crap better.
<this is truly not necessary and generally overcomplicates plumbing. From an aesthetic point of view if none other. Easier and safer/better movement of detritus can be obtained simply by having adequate water flow in the aquarium that keeps all in suspension. In fact, the presence of much solid matter on the bottom is an indication of inadequate water flow>
Thus we produced a U-tube that sucked the water up to the surface, went through 180 degrees and then drained downward through the bulkhead.
<U-tubes are patently flawed and potentially (easily) prone to failure>
We had no overflow boxes or filtration from the top of the tank. A hole of variable size was drilled in the very top of the tube, thus connecting to the air. The height of the tube determined how high you wanted the water level in your tank. The nice thing was that with a power failure the water only dropped to bottom of the U and then stopped flowing.
<yes... but it can break siphon, and when the power resumes, the display overflows>
Secondly the faster your pump worked the quieter it became because the water rose just above the air hole and occluded it. A pump with excess capacity would have to be gated to rate. Apart from the crap aesthetics can you see any major problems with this?
<they very commonly overflow the display when the power resumes. I have often jokes that I will not sleep in a house with a u-tube on the tank: fire hazard>
I am currently getting back into the hobby with a 135 g. I am going to phone the local physics professor and ask him to calculate the flow for a 1 1/2 " U-tube. Do you know of any company who could make a clear plastic U like that?. Many thanks. Barry
<my strong advice is to have a proper/modern overflow hole drilled on the back wall of the tank (high) and sleep in peace :) Best regards, Anthony>

-CPR overflows-
Hello WWM, I was read the FAQs today & saw this statement from Kevin, concerning CPR overflows-->"<I'm a J tube user for life (if drilling isn't an option!), the CPR overflows are horrid, and I'm not sure about the Tidepool ones as I haven't used them> <-- What makes the CPR overflows "horrid"? Just curious, I was thinking about getting the 1400gph CPR overflow myself!
<Heh, I knew I'd have to explain sooner or later. I've used the CS90 and CS102 (the 1400gph one you're talking about) both on my personal tank and at the shop. My main reason for disliking them is that a small pump w/ venturi kit is required in many cases to suck the accumulating air out of the top of the siphon "chamber". This pump then spits the bubbles into your main tank, that is, if it keeps sucking the air out because, w/out frequent cleaning, the nipple provided to suck the air out get's clogged. When this happens the chamber will eventually fill with air; breaking the siphon. Although I have had bad experiences with them, not all have, and some actually swear by them. A quick ReefCentral or reefs.org search will get you several more opinions on the subject. Personally, I find that the additional cost and potential problems make a J tube style overflow choice a no-brainer. If you wanted to try a CS series overflow, make sure you match the flow closely, and be willing to deal with the unique issues surrounding it. Hope this helps! -Kevin>
Thanks, as always, Scott in Denver

- Overflow Design -
Hello Bob! - Please forgive the intrusion, I do normally post my questions to the "Crew" in general. <Well, it's JasonC here this time... hope you don't mind.> I'm looking for help with designing the overflow/s for my aquarium.  I'm in the process of establishing a new reef setup (seam rupture on previous 14 yr. old tank) that will be installed in a wall and viewed from two sides.  I awaiting the arrival of a 375 gal. acrylic aquarium from Tenecor (ships next week) which I ordered sans overflows.  I did this because my plan was (is) to utilize some type of "external" overflow system.  The dimensions of the tank are 96x30x30x3/4, of course the overflows will be installed on the end, or ends.  My idea is to drill a series of holes at the top two inches of the tank to function like the teeth on an internal overflow, and attach the overflow box (drilled for bulkheads - 2 x 2") to the outside of the tank.  If this sounds feasible to you, what would your recommendation be for the size of the skimmer holes? <It's kind of a sketchy plan... you will need to 'attach' the overflow box just as if it were part of the tank - with acrylic cement, otherwise it's going to fall off... you should consider just having this built onto the tank.> How many and how far apart (without compromising structural integrity)? <I'd go with 1/4-3/8" holes, as many as you want, not too close to any seam or edge.> What's the max flow I could expect through these holes? <Depends on how many you drill, but the number would be pretty high to match your expectations... perhaps 20-30 per end.> How big should the skimmer box be to handle the flow (say - max 2000gph)? <Well... drilling small holes isn't going to get you this high a flow rate unless you drill a lot of them - with standard bulkheads you need two to three 1.5" holes to reach a flow rate that high. Additionally, flowing this much water in and out of the tank is going to be very noisy... I would consider lowering the recycle rate in favor of some strong water movement within the tank via strong powerheads like the Tunze Stream Pumps.> Thickness of the acrylic? <I assume you mean for the overflow box... 1/4" would work - doesn't need to be heavy duty because it won't be holding much water at any given time. And... as I mentioned before, you will have to bond this to the tank with acrylic cement.> Have I missed anything >:-) <How about three large holes with bulkheads and strainers, plumbed directly to your sump?> If you think this is a bad idea my second choice would be to utilize an overflow design like Anthony describes in his coral propagation book. <I'd rather see you do this.> Saying that, what would be the measurements of this design? <The same as the width of your tank.> I would want to keep the dimensions to a minimum for aesthetic purposes. <Again, and I think we've discussed this design before... you should really be working with the people at Tenecor to help you realize this design rather than trying to augment the tank after its arrival. Add a couple of inches the length and this portion will be hidden behind the wall - this way you can have either a standard overflow on each end or perhaps something similar to Anthony's design. Any attempt to attach something to the side of your tank is ill-advised - if you have little or no experience with acrylic adhesives, you could potentially ruin your tank if you are not careful. If you've never worked with acrylic before, it's actually not that easy to make a five-sided box that doesn't leak - and you're talking about a four-sided box that needs to be attached to the tank.> If you have other ideas please feel free to expound. <My thinking here is that you should just keep it simple - drill two 1-1.5" holes on both ends - add bulkheads with strainers, and plumb these to your filtration system.> Any assistance will be greatly appreciated.
Respectfully,
Eric
<Cheers, J -- >

Overflowing With Ideas... (Prefab Overflows)
I have constructed a tank and drilled the holes in the bottom for a
wet/dry filter but cannot find a supplier for the overflow. Do you know of a company that sells the overflow by itself or in a kit with some other plumbing parts?
Thanks Jerod
<Yes, actually. There is a company called "wetdryfilter.com", and the owner, a friendly hobbyist named Christian, can custom fabricate overflow boxes to your tank's specific parameters. He's honest, and does good work. You can find designs on how to construct your own standpipe unit by searching on the net for the "Durso standpipe", or you can purchase one from the man himself...Good luck! Regards, Scott F>

Drill or overflow?
Hi all,
I have a 90 gallon glass tank that I need to set up for a wet/dry filter w/sump.  There is a LFS that will drill it for me for $50.  This expense, plus the cost of bulkheads etc. will about equal what I would pay for a good hang-on overflow setup.  Which option do you think would be preferable? <drill it>  Any particular weaknesses of either way?   Appreciate any direction you could provide.
Thanks,
Jim
<Hey Jim, I'd go with the drilled overflow, the hang on type will fail sooner or later and leave you with soggy floors. -Gage>

Pre filter/skimmer J-tubes losing prime
[AKA... you can't polish a turd]
Jason C, could you please forward this email to a few of the other members of the organization? Perhaps they may have an alternative method to fix this problem that you may not be aware of.  I mean, it IS possible.
<at your request, your message has been forwarded to me, bud. Anthony Calfo in your service>
I was thinking that perhaps extending the J-tubes by about an inch or so into the intake compartment may help keep them deeper, so that when the power fails and the little intake drains to a certain point, the J-tubes would still be below the surface of the water.
<J-tubes are inherently flawed and inferior devices. I'm not exaggerating when I say that I would not sleep in a house with this application. In ten years I have heard of numerous failures by siphon overflows, and two of them caused house fires. Better designs may carry you a year or two... even three before a failure. But then again... maybe not. There are modifications of the design that include drilling and tapping the top of the tube with a check valve and airline. This is then connected to the venturi of a powerhead to help prevent the siphon from breaking. It is helpful but hokey. It relies on the power head restarting after a power outage, and some do not. The venturis clog fairly quickly and often. And even when the best modifications and performance of a siphon overflow are in place, it can be wrecked in an instant by a low running sump that throws bubbles into the main display or even the literal addition of an airstone or PH venturi in the tank. Any bubbles that reach the surface can be overflow and overwhelm the j-tube... breaking siphon. The moral of the story... "You can't polish a turd". I would rather not have a sump or trickle filter than be forced to live with a j-tube. Sorry, bud... it is what it is>
It's things like that that I'd like confirmation on.
<understood and agreed>
I'm just guessing that it might work.  
<I'm sure it will fail in time. I have yet to see a modification for three years without a catastrophic event. Most don't even make it to one. Case in point, how many overflows have you had already?>
Please don't reply "Well try it and see".  
<no worries here... I'm suggesting you drill the tank or drill the sump/trickle and treat it like an upstream refugium (mount it above the display and pump up to it, letting water overflow down and the display becomes the sump>
I just wanted a few more opinions from the staff on your end.  Maybe they've encountered similar problems with the J-tube
<yep... about 15 years worth including an investment into a commercial j-tube set-up for about 1000 gallons worth of breeder tanks>
arrangement and KNOW what seems to remedy the situation.
<yep... remove it ASAP my friend>
Thank you for all of your assistance. Steve
<best regards... wish I could have borne better news for you. You have your work cut out for you, bud. Find whoever suggested this j-tube to you by the way and kick them in the jimmy. Drilled overflows have been the mainstay for a decade. Anthony>

Overflow via Durso vs. Back Wall....
Greetings to WWM,
If you were setting up a new tank which would you go with... Either 2 1.5" overflows w/Durso standpipes or a couple of bulkheads at the top back of the tank?
<Either will do the same thing. One is less expensive than the other unless you use overflow boxes in which case they are roughly equal in cost/flow/noise, depending on size (of box and plumbing/bulkheads), depth (of overflow box and how far, if any distance, the water falls into the boxes.>
Rather than personal preference I am looking for the configuration which will A. minimize the amount of overflow in the case of power outage and B. minimize the amount of noise.
<This depends on how the boxes are set-up and the height of the overflows/Durso pipes. The water will only drain as far as the top of the overflows unless it is designed differently AND if there are holes drilled in the *pump returns* just below regular operating water level so the pump return doesn't also siphon water into the sump, backwards through the pump.>
Is there an inherent problem with having your gravity fed overflows high on the back of the tank?
<No, unless you want to make them adjustable, in which case having a 90 degree ell (coming out of the bulkheads) and perhaps a threaded screen/pvc fitting will allow you to raise and lower them to the desired height.>
I built a sump/refugium this weekend of about 18" in height and my first baffle is 14" tall so it doesn't have a lot of room in case of power outage which led me to the back drilled idea... any comments, suggestions?
Thanks Guys! You're invaluable!
<Just remember, gravity and siphons are very reliable. Make it work for you!  Let us know if you need more assistance.  Craig>

Re: Overflow Question
I'm looking into replacing my current 180 gallon aquarium with a new one. Would like to know the differences between the standard corner in tank overflow versus using standard 2" bulkheads (x3) drilled into the back wall along the top at water level. Obviously both will serve the sump below the tank. The main thing I'm concerned with is the noise level. The corner overflow in the current tank uses a Durso stand pipe, so it's relatively
quiet already. Sincerely, Craig
<There is no real difference between the two. The bulkheads can also be enclosed in a skimmer box like the corner boxes if you wish. The noise depends on how the overflows are vented and the size of the overflows/boxes, and how far the water falls into the overflows/boxes, if used. Hope this helps you out!  Craig>

Overflow modification
Hello again...
<cheers>
I have a question about one of the FAQ's I read in regards to the overflow described in Anthony's book.  The person wrote that he wanted to set his tank up without the overflow box on the upper back wall, just have the bulkhead holes with screens over them.  My question is, won't this keep the water level too low?  
<Well... it could be too low for aesthetics IMO and it would at that point have none of the benefits of the horizontal overflow described in my book. It would simply be a traditional bulkhead application. Those bulkheads  could simply have an elbow with a screen strainer turned upwards to raise the water level (and in fact give control over changing that level by swiveling the elbows higher or lower... some advantage there)>
If you have 4 1.5" holes about 3" to 4" from the top to the center of the hole, the water level will never climb much higher than that, right?  
<correct if screen only are used... but elbows with screens can correct that (raise water level)>
If you do fabricate one of these overflows, I assume then that it should only touch the back wall,
<capturing the bulkheads yes>
hence your reference in my prior email to it being almost 48" in length.  
<indeed.. thinning the overflow water and improving proteins collected>
Then I don't have to worry about the tank bowing and the overflow separating from one of the walls, correct?
<correct... the flow of the long horizontal overflow is a tremendous support... prevents bowing>
Thank you!
<Best regards, Anthony>

Almost made a big mistake (big tank plumbing)
First off I'd like to say that today was the first time I've visited your site and I'm totally blown away by the wealth of information offered.  I will definitely make this my first (and quite possibly ONLY) destination when posed with aquaria-related problems.
That said, I am building a 300gal "freshie" tank to house my ever-growing Clown Knife, and would like to bounce my ideas off someone who knows their schtuff.
My original plan incorporated a CPR Overflow Bow with two 1" outflow bulkheads rated at 1400 GPM.
<Mmm, do make this two overflow boxes... just in case one fails... you are likely familiar with how "frisky" Clown knives can be during the night... One unlucky swipe at the single box might knock it out of commission... the pump/s below will continue pumping, overflow the main tank, drain the sump/s...>
The 1" lines would run to two separate 30gal sumps, each containing a Quiet One Pump (an okay choice for freshwater I'm assuming).
<Yes... but please do check around re this pumps reliability... and consider other makes. The bulletin boards are great here for input. Ours: http://wetwebfotos.com/talk/>
The pumps(2) are rated at 750GPM at 4' head height, so with my head height of 5.5' I was counting on getting that down to under 700GPM per pump so that the CPR would keep up.
<Best to tie those sumps together (thru-hulls, pipe) in case of mechanical failures... am an old worry-wart with plenty of water damage clean-up experience...>
Now my problem: I've read over and over that siphon tubes (especially the CPR models) are nothing but trouble waiting to happen.  I am re-designing my setup to incorporate holes drilled into the back of the tank just below water level to allow gravity flow to the sumps (which will be easy as my tank is of mostly wood construction w/glass front).  Since the CPR box has two 1" bulkheads, and claims a 1400GPM flow rate, am I wrong in assuming that two 1" holes drilled in my tank will provide the same flow?
<Please oversize them... 1 1/2" inside diameter is much better... easier to arrange to not make a bunch of noise>
Also, if the holes are below the water line, and I make them too big, wouldn't that cause more water to enter the sumps than the pump could remove, causing sump overflow?
<Mmm, no... at least if you don't "overfill" the sumps... the amount of water "in play" is all you're concerned with. Start the pumps with the sump and main tank full, mark the sumps at the level they drain down to with the pumps on, and never fill the sumps beyond this level... the transit volume of water is the difference in starting, pumping levels>
Would using ball valves on the line to the sump and the line to the return head allow me to achieve a balance?
<Don't count on this... or even float valves... count on gravity and what sources of blockage, trouble you can anticipate. Bob Fenner>
Thanks for your help,
Brand Smith - Anderson, Indiana

Re: Skimmer Box / Overflow design
Hello WWM Crew!
I'm pondering an approach to get water out of my tank and into the sump without using a siphon-based design and without drilling the bottom of my tank.
I've attached a design in both PDF and JPEG format and I'm hoping you can give it a sanity check. The goals are to achieve a good flow and to minimize noise.  A couple of points I'm wondering about are:
- Is the (downward pointing) elbow in the skimmer box necessary,
desirable, or irrelevant? (I borrowed it from the Durso design without really knowing why)
<It's not necessary, but reduces sucking air sounds at water surface, esp. if the skimmer box has enough capacity to feed bulkhead flow. Box size should be large enough to accommodate flow, plus. The deeper in the box the bulkhead is placed, the less this is needed.  They sell bulkheads with screened intakes which could/should replace the filter/screen/light grid idea which will cause problems. Install a drip plate in the sump if you want this.>
- Is the tee with vented cap necessary, desirable, or irrelevant?
<Absolutely, this is where the venting/air will come from with a submerged bulkhead skimmer box/intake, so the water can drain into the sump.>
- Should the tee w/ cap extend above the top of the skimmer box teeth?
<It should rise above tank water level/skimmer box teeth by a few inches or water will drain out of the vent.....>
- Would fixing an air valve into the cap to allow adjustment of airflow be a good idea?
<Nope, you want a 1/4" hole that will allow air to enter and exit at will. The air must pass through this hole to equalize the pressure in the drain.>
- Should the outtake, tee, & drain pipe be the same size or should there be a reduction/enlargement somewhere?
<These can all be the same size, as long as they are sized for the desired flow rate.>
- Is having a pre-filter here a good idea? I like the idea of keeping gross objects out of the sump & drain line with the understanding that the pad or piece of foam will need to be rinsed frequently.
<Try a micron bag or drip plate in the sump instead.>
- If so, is a simple piece of light diffuser (egg crate) resting on small ledges inside the box a reasonable choice for supporting the filter media? Is this material generally considered to be aquarium-safe?
<Yep, as above.>
- Assuming a bulkhead sized for a 1.25" opening, how deep would you make the skimmer box and where in relation to the top of the box (waterline?) would you make the centerline of the outtake pipe?
<Many make these full tank depth. The depth is related to overall skimmer box size/capacity to feed the bulkhead water without sucking air at water surface or outpacing the box capacity. This is also true of bulkhead depth. The large the box and deeper the bulkhead, the better.  Some skimmer boxes run the full length of the tank. I would prefer a deeper box and bulkhead near the bottom. In the event of power outages, the water will stop siphoning at the bottom of the box teeth. You don't supply tank size or flow rate, just oversize box and plumbing to accommodate needed flow rate. Shop siphon type overflows to see what plumbing sizes/capacities they use.>
Well, that's it. Any other thoughts or comments you might have are highly welcome. Thanks as always, Tim
<Looks good Tim, have fun!  Craig>

Overflow Prefilter
Greetings,
<<Hi, Don this afternoon>>
Always a pleasure to read this web-site.  It is great to see that you have some more "Pros" other than Steven helping out. yuk yuk yuk! <<uh, Thanks, I think, Oh, Pro, now I get it;)>>
I have a overflow box that has a coarse sponge pre-filter.  I typically rinse this about once a week.  It always has some decaying food and mulm attached to it.  I think that it needs to be cleaned more frequently maybe even daily.  For a lot of reasons like travel and procrastination, daily cleaning of this pre-filter won't happen.  What are my options?  The overflow feeds into the sump where I have a protein skimmer.  Should I remove the coarse pre-filter to provide more "raw" water to the protein skimmer?  <<Recommended course. See here for more http://www.wetwebmedia.com/marmechf1.htm>> Knowing that food gets caught on the pre-filter....will the protein skimmer collect the food or will the decaying food just get moved to the next coarse pre-filter just before before the return pump? <<Ahh, maintenance never stops eh? You can try a micron bag on the end of the overflow into the sump to catch crud, but it too will require regular (every other day if not every day) maintenance. Maybe best to go without either and try to get to the other filter more often. >>
Also,
I would like to drill the 40 gal glass tank for a 1" overflow.<<Just an observation as I don’t know what your intentions are, but maybe two holes? easier now than breaking it down, again, later>>   My understanding for this procedure if you do not want to remove everything from the tank and there is adequate space to drill the hole is:
1.  Drain the tank well below the overflow - add filtration and heat to the lowered water
2.  Clean the inside surface where the overflow box will be mounted
3.  Silicone the overflow box 8"W X 5"H X 3"D in place
4.  Drill the hole using the overflow box to catch debris on the inside of the tank
5.  Install the bulkhead in the hole ensure that the bulkhead id is at least 1"
6.  Attach plumbing to the bulkhead to the sump
7.  Ensure that the silicon is dry (6-8 hrs) <<I would wait 24 for any silicon job>>
8.  Re-fill the tank and restore heat and filtration in the sump.
Where is the best place to get the glass bit and lubricant?  <<I used water>> Is the above too risky?  I do have a 20 gal tank that would be ready in case of a serious (i.e. crack) situation.<<While the above may work and for others successfully, I  would not advise to drill anything but an empty (completely) tank. I got the first hole drilled in a 20H for a refugium and about half way through the second, BOOM, well, lets say I then waited for the glass shop to get a replacement cut for me. I got a bit locally, but there are many web sites selling them. Google search? Also, see if you have a marine society in your area, they may have some you can rent/borrow>>
Again, thanks for the help.
<< Happy glass drilling Don>>
Kinzie

DIY overflow box
Real quick one here.  I have 2 1.5" bulkheads on the back of my tank, and about 3" or so from the top of tank.  I have added some 90 degree elbows to function as overflows and surface skim.  I got to thinking tonight.  I have a lot of extra acrylic from my sump I made, and thought...maybe I could make some overflow type boxes to put around the bulkheads.  What do you think?  can this be done?  Main problem I'm having is how to attach around the bulkheads so flow only comes over the top of overflow.  any suggestions?
<< Hi Bryan, Oh YEAH this is a good idea. Make a slotted dam/weir along the back wall deep enough to accommodate the bulkheads, elbows. Quite beneficial. See here for ideas http://www.wetwebmedia.com/plumbingmarart.htm. Note on the diagram that you can extend the bottom of the internal skimmer box and make a shelf for coral, etc to help hide the box. You say 'around the bulkhead'. You want to skim as much surface as possible. A small 4-5" box around each bulkhead is not going to do nearly as much good as one the length of the tank.
Gonna make a leap here, the tank is also acrylic? You can try silicon, may not hold acrylic. If not, me thinks the next step is 'gluing' with acrylic solvent.>>
Thanks Bryan
<<My pleasure, Don>>

Re: DIY bulkhead overflow
HI guys,
Don thanks for the support about my bulkhead overflow idea.  <<My pleasure, glad you were able to follow the ramblings of an old man>> I had thought about just placing a box around each bulkhead, but then Don made comment, and I remember Anthony touched on in his book, that an overflow the length of the back of the tank is a lot more efficient.  So...I did some measuring today to start making plans.  This is what I have so far.  I have a glass 75 gallon tank w/ 2 1.5" bulkheads about 3" from the top of tank on each end.  I want to make this out of acrylic.  The overflow about 44" across to each side, roughly 5.5" tall/high and the top lip of overflow about 3/4" or so from the top of the tank.
This is where I need a little help.  How wide/ deep should this thing be?  <<Obviously, enough to handle the elbows. 4x4 or 5x5 I would think. Unless I am missing something here>>I remember my CPR siphon overflow and even though it hung on the tank the overflow part was probably 1/2" or so wide where the water flow was.  So I was thinking between 1/2" and an 1".  This is the big question.  How to attach to the tank?  Right now I'm thinking about adding/connecting 1/4" to 1/2" edges/strips to the back of the overflow that I described above, so that now, I only have to silicone 3 edges to the tank (2 sides and the bottom)...(hope you can follow) instead of a whole big piece the length of the tank.  How does this sound? << Sorry Bryan, can’t say I have ever read/heard positive thoughts about using silicon to attach acrylic to glass. I would think you would be better off using glass. Or, figure a way to support the acrylic overflow with brackets>>
any suggestions/comments?  See any problems or change
anything?  Thanks Bryan <<Sorry I didn’t have better news, Don>>
P.S Craig, the elbows on my bulkheads worked.  I filled the tank like you said and everything leveled out. sump and main.  Thanks for your help. <<Ain’t he something :)>>

Re: DIY bulkhead overflow (part III)
Don thanks for quick response about my DIY acrylic overflow for my bulkheads.  <<Glad to help>> Let me run a couple more things by you.  <Walk please, I’m an old man and can’t keep up>> I forgot to add that I 'm not going to
use the 90 degree elbows on the bulkheads with my overflow. <<OK>>  I thought that this would make it not as wide/big.  Have the bulkheads open or bare and let the flow go over the acrylic overflow and down the bulkheads to the sump.  <<Ahh, good>> (this way I can make it say 1/2" to 1" wide and won't take up a lot of room or be that noticeable.)  Does this sound fine or are there any problems you foresee? <<IMO it is better to over design than under. Last thing I want to do is tear down/redo stuff. Experimentation is good though too. Let me know how this works for you>> I was a little disappointed that people don't have luck with glass to acrylic silicone contacts, sooooo, back to the drawing board.
OK I'm at the drawing board, <<Quick Trip!>> what about this?  Add or put brackets to the overflow so that its main support is by the brackets on the tank, then use silicone around the edges of the overflow so that flow does not seep in around the sides  (only over the top) and that way if in the event of a power outage there is no flooding of water seeping through the sides of overflow down the bulkheads and into the sump.  Does this sound like it might work? <<Again, hate to be the devil’s advocate, but remember Murphy? Well, when the thing misfires, if it ever does, it is gonna be while you are asleep or at work. At least that is my luck :(>>
Oh yea, last thing.  I posted this overflow idea on reef central and someone thought I was crazy for wanting to do this b/c I should be getting enough surface skimming from my bulkheads and elbows, what do you think?  <<To each his/her own. Different folks, different experiences. Maybe you should try the open bulkheads first and see if that works for you. Make sure to screen for livestock benefit. Add the overflow later if the open bulkheads are not to your liking>>Thanks Bryan <<Forge on, and let me know how it comes out, what you decide. Don>>

- 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 -- >

Overflow question
Hello Crew-
<cheers, mate>
I am writing because I read tonight's daily questions and answers and learned a lot about building my own overflows. I have a 55 gallon tank that I would like to have drilled. My question is if I am drilling the back top of the tank do I have to make a dam or box to cover it?
<not necessary... just an enhancement. It concentrates proteins by stretching the overflowing water collected (proteins concentrate in the surface-most layer of water)>
Can I just have the tank drilled and the hole covered with screen?
<absolutely! You will not even notice or appreciate the difference/benefit of an internal horizontal overflow if your tank load is very light or you can otherwise aggressively control nutrient levels (wicked skimmer, large water changes, careful feeding, etc)>
I guess I just want to know if the only reason I would need to build a dam would be to keep fish or coral sucked up into it. Can it be done without safely?
<either way is fine... the course screen cones on the bulkheads are good for deflecting macro-organisms>
Thanks! Your site rocks and I have Bob's and Anthony's books. I have learned a lot. Josh
<thanks kindly. Rock on my brother :) Anthony>

Overflows and Refugium
Hello, I have a 120 gal tank with one overflow going to a sump with a mag drive 500gph. My question is can I add another overflow to go to a 10 gal refugium with a smaller pump or will it overflow.
<its not clear what you mean here? A second drilled hole overflowing to the refugium  but still draining to the main sump? If so, yes... will be fine. You mention another pump though? Does this mean a second pump returning the water back to the display from the refugium which acts instead like a second sump. If that's the case... no way, a danger. You best bet is to simply tap a refugium inline on the way down to the sump (or atop above the display and the refugium will overflow back in>
Also would a 36watt pc 50/50 be sufficient for a refugium with macro algae, live rock, polyps, and mushrooms?
<if said vessel was very shallow (12" or less). Anthony>

Overflow Design
In some of the FAQ's that talk about overflow's, Anthony mentions having holes drilled from the back as opposed to the bottom for water going to the sump.  
<correct>
Was I misreading this ( it was pretty late and there are INFINITE faq's! ) or is there a reason why this would be better?  
<yes, my friend. Beyond aesthetics (taking up far less space than those awful noisy and inferior overflow towers with holes drilled in the floor)... there is the advantage/option of building an internal Horizontal overflow box that contains the holes drilled in the back wall. This will skim far more concentrated protein-rich surface water than the same holes fed by a vertical/tower overflow or standpipe. This will improve the performance of you skimmer miraculously and lead to much better water quality. There are diagrams of this in my Book of Coral Propagation. I haven't had updated scans made yet (brother-in-law will draft them for me in AutoCAD soon, I suppose). In the meantime I can fax you some scrappy hand-drawn pics to spare you from buying my book :) >
As for a pump used for circulation on a closed loop ( I am assuming the closed loop reference is from tank through pump back to tank ),
<exactly correct... a fairly effective and necessary evil for some tanks with SPS corals in particular>
if pulling water from the overflow box area poses the problem of too many microbubbles, is it better to just have some intakes drilled in the back about halfway down to the bottom?
<it works but that isn't my preference... I have no problems with microbubbles on a well designed system: a diffusive skimmer box or partition in the sump breaks incoming bubbles, baffles before sump pump deflect most others, and all remaining can be off gassed in a small upstream refugium (the best placement IMO) before overflowing to the main tank>>
Will there be too much suction there at the entry points, possibly pulling in snails, etc (it would be covered  of course)?.  
<yes... quite dangerous. Requires a course mesh/screen that is accessible>
In the faq's, I read something about a 1" hole producing about 300 gph in the overflow.  
<correct... a realistically quiet and safe volume... although at a noisy and precarious rate (suction) they may actually do over 500GPH>
If I want to have a pump that can handle about 1000 gph on the return, what can I do?  
<that would be four 1" holes bub>
Most of the pumps I have seen talk of fittings for 1" PVC.  Can I make a larger hole in the overflow from the tank, like 2" that eventually sizes down to 1".  Will this help or do I lose the benefits of the bigger hole at the 1" fitting.
<correct>
Or could I have multiple holes, although the overflow box may not be big enough for this.
<Ahah! Exactly the problem with those crappy commercial aquariums with internal overflow towers that claim to be "reef ready"! It's one of my common rants here on the daily FAQs. Hence one of the advantages to a horizontal overflow on the back of the tank. It is explained concisely, I think <G>, in the book passage... fairly obvious in the sketch>
I hope I haven't filled my questions quota,
<not at all... I really wasn't paying attention as I typed anyway <G> as evidenced by misspellings and clumsy skills as a typist>
but I want to make sure the next tank I plan to get is done RIGHT, or at least as close a possible.  I have spent a fortune on errors! Thank you. Paul T
<best regards, Anthony>

- A 'brief question - Pre filter/skimmer J-tubes losing prime
<Greetings, JasonC here...>
Hello and thank you so very much for providing the time to answer so many repetitive questions for all of
us reef lovers  :-)
I'll try to make this brief so we can get right to the meat of my problem. <I looked ahead... it's not exactly what I would call brief ;-) >
I have a 55 gallon acrylic fish/live rock/coral salt water aquarium with wet-dry sump (minus bio balls as
this was causing a nitrate' fest so I pulled em out).
The sump has a Berlin turbo skimmer and a few power heads for circulation and one leading to a 10 gallon
refugium I have set up in the adjoining cabinet about 3 feet away with a gravity fed return to the main
sump.  The refugium is on a reverse daylight schedule and houses Chaetomorpha macro algae, as I am not a big fan of Caulerpa and all of the toxic headaches it has caused so many others in the hobby-addiction :-P
Anyway, my problem is this....
I have the "dreaded" hang on the back prefilter box with two "J"-tubes as suction, leading down two 1 1/4"
drain hoses into my trickle filter in the sump.
Problem is, ........POWER FAILURES
Ughhhhh!!!
What happens is that the J-tubes seem to lose their prime when the power goes out, and the tubes partially
empty, or sometimes fully empty. <That is the nature of the beast.>
Then when the power comes back on, the return sump pump begins pumping water into the main tank and the
tank overflows all 10-15 gallons of sump water all over my wood floor.
Yes, ...that's what I love the most...warped wood.
Anyway, I'm just not up to draining the main tank completely and drilling a bulk head fitting with a
stand pipe and some form of internal filter box siliconed to the inside of the tank.  I just cant do
it. <Then instead perhaps you'll enjoy replacing the floors more so...>
So, I am asking your professional opinion on how I can remedy this situation of the J-tubes losing their
prime in the hang on back prefilter/skimmer. <You can't...>
It's a typical setup that comes with most pre made wet/dry systems. you know...comes complete with the
twin black drain hoses, etc.
If you don't think you can come up with some type of reconfiguration of the J-tubes and housing, then
perhaps I'll have to resort to the disgusting method of rigging a power head from the main tank via a tube
into the sump, so that when power returns, at least the tank will have water "pumped" back into the sump.
That's VERY unsightly and am hoping to get around having to do that. <You could always drill the tank ;-) >
Please help if you can. <I think you already have a good grasp on how you can help yourself.>
Warmest regards, and thank you again for providing assistance to those of us in need.
Steve
<Cheers, J -- >

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>

Overflow to sump & gph to and fro
Hello All/Some/One:
I read in section http://www.wetwebmedia.com/pbfaq6mar.htm where Mr. Pro (stage name?) wrote: "I  would not take a siphon overflow for free and I would never even think about using one in my house".  If you are not Mr. Pro, do you agree?  Is the actual problem of breaking siphon that the sump's contents will then be emptied and cause the display tank to overflow?
<Nope, the opposite>
If so, what is a person to do with a 55gal all-glass that is already set up, but is now looking into sumps/refugiums?  At this time, I am not ready/willing to break it down, bring it to a professional, have holes drilled and an overflow put in (which I also read that they may not even drill/warranty my tempered-glass bottom!).  Can a safety switch be purchased (or created) that when the water level reaches critical in the display, the pump will shut off?  Please help with some solution other than "get yourself a tank with a built in overflow" wink!).  Also, please clear this up for me;
if I have 1000gph overflow to sump, and 600gph return pump, does the overflow part slow down?
<Yes, the overflow can only remove as much water as is being returned to the tank.>
How about the opposite: 600gph overflow and 1000gph pump?
<This would be a waste of pump, the overflow would be too restricting.>
Or does neither work and they need to be equal (can't be, right?)?  I have read so many FAQ's that I think I am confused again. Regards, Rich.
<Hey Rich, drilled overflows are always going to be safer than siphon overflows.  The problem with siphon overflows is the potential for problem.  In theory they work well, say for example your power goes out and your pump stops, then the tank drains down to the level of the overflow box that is positioned on the inside of the tank.  But what if the suction cups that hold it to the glass are old and no longer fit tight, then water will suck through these holes and overflow your sump.  Or maybe the return from the pump starts siphoning water back into the sump in the even of a power failure, another chance for your sump to overflow.  Another problem is air gathering in the top of the siphon tube and breaking the siphon, then the pump drains the sump and burns up.  
Than being said, make sure that the suction cups fit tight, drill a small hole just below the water line on the return to the tank to break the siphon in case of a power failure.  You can also drill and attach some airline tubing to the top of the siphon tube and attach the other end to the Venturi portion of a power head, so if air does gather it will be sucked out.  Hope this helps. -Gage>

Overflows & FYI
I have a 100 gallon acrylic tank with two overflows; opposite each other, on the right and left side of the tank. Since I bought the tank, one of the overflows has never really worked. I've had the tank for a year but recently I've been redoing a few things and the "dead" overflow is bugging me. I've tried all of the usual things. . .bled the return lines checking for clogs, etc. No success. As a side note, I'll also mention that the return line is not equal distance from the overflows. Picture this: the tank and stand are 60" long. The sump stretches across half of the sixty inches. The pump plus the exit line from the sump covers most of the remaining thirty inches. Naturally, the overflow on the right side of the tank is closer to the pump than the left side. 
<should be of little matter on a level tank>
However, oddly enough, it is obvious to me there is more water coming out of the left return line than the right. But it's the right overflow that works the best! Are you confused yet? 
<yep>
It appears to me that the left hand return is shooting water through the right overflow. This is not happening in the reverse.
<er...OK>
I though that overflows worked on the principle that the water level of the tank was supposed increase thereby gently spilling water into the overflow. 
<again... on a level tank... the drop should be relatively even if the run is also similar enough (which it is likely to be from the bottom of each overflow. You don't have either (especially the slow one) releasing into the sump below the sump water level? Impedance>
The tank has way too much surface agitation for the water to gently overflow. Any suggestions (short of draining the tank, etc.) to solve this problem? Oh, the system pump is rated at 1500 gph but it's going through a 3/4'' line and changes to 1/2'' line as the water enters the tank. 
<restricted indeed! Do you need to? why not more flow (larger supply line)?>
This tank was a Clear View aquarium design. I would never have had lines that small.
<perhaps re-route the return with a simply flexible line off the pump and a u-tube over the top of the tank... even if only as an experiment>
On another note. . . In the past, I have read many questions from people that own the Turboflotor 1000 skimmer. I have always been unhappy with mine (almost a year) until this week. 
<if you aren't feeding this skimmer from a skimmer box in the sump with a static water level, then that has been most of the problem>
Let me give a little advice: 1) Use a skimmer box to keep the water level around the skimmer between 10 and 15 centimeters, no more no less; 
<ah-ha!>
2) if you've been using the skimmer, check for a clogged venturi, clogged feeder pump, or problem with the Rio 2600.
<good advice.... thank you>
I assure you, those two items alone will make a world of difference in the skimmer's performance, especially the skimmer box.
<agreed... critical for all skimmers. A skimmer getting water from a pump/sump with a fluctuating water level is a great impediment!>
Keep up the good work and thanks for your help! David D.
<thanks kindly, Anthony>

Re: Overflows & FYI
<<You don't have the drains releasing into the sump below the sump water level do you? Impedance>>
++++I'm not sure I follow. The sump is a homemade Rubbermaid. The overflow lines empty into the skimmer box about a 1/2'' below the water level. The lines simply rest slightly below the surface of the water. 
<exactly as stated/feared above... in doing so air gets trapped and backed up. Overflow drains should never be even slightly under water. Release a whisker just above the water if you must be close but let the air escape... else it backs up flow>
Are you suggesting an improvement? I'm game if it might help the problem.
<as per above>
<<perhaps re-route the return with a simply flexible line off the pump and a u-tube over the top of the tank... even if only as an experiment>>
++++Might be worth a try. But if the u-tube were to get loose. . .
<sheesh... a hard U-tube bud clipped or clamped to the top... its just an experiment :) Be resourceful, my friend>
I might also mention that I get a suction noise from the left return from inside the tank. This is not the flushing toilet sound that one gets from the overflow. I built a Durso style silencer when I first got the tank and it's been wonderful. The sound only happens maybe every twenty or thirty minutes. It looks like a little cyclone is forming right where the water leaves the flared nozzle and enters the tank. I have helped the problem immensely by turning the return nozzle clockwise. I just thought this might help give
you another clue as to what the problem is. Maybe I should just leave well enough alone and continue using those powerheads. I appreciate your thoughts and efforts. Thanks again.
<the flushing toilet noise is often trapped air... the cyclone is usually an undersized overflow drain or and oversized pump. Undersized commercial overflows are a dreadfully common problem. Few can ever handle reef sized pumps. Best regards, Anthony>

Overflow
<<Greetings, JasonC here...>>
I have a 20 hex I am going to use for a refugium and you said "PLEASE don't use a siphon overflow, drill the tank." What is your aversion to siphon overflows? <<They clog very often and need regular cleaning. The clogging can/will cause the tank to overflow and perhaps your return pump to run dry.>> I am looking for some advice as to where to drill the holes into the back of the tank to install the overflows? My guess is as close to the top frame as possible leaving enough clearance so the
bulkhead fitting will clear the frame, is that correct? <<Yes, would be my choice.>> My LFS (189 miles away) has only drilled the bottom of tanks and did not have any ideas where the holes should be drilled in the back of the tanks. I am very limited on the size of the hole I can have drilled. My community is very small and only on glass shop drills glass. Fortunately, they can drill 1 ½" holes. I know this probably seems like a stupid question, but I have already made enough mistakes, I don't want to make another by ruining a perfectly good tank <<Not a stupid question at all. Cheers, J -- >>

Overflow Question
Greetings,
I have been experimenting with different ways of quieting my overflow before I complete the setup of my pre-drilled, 72 gallon, bow-front All-glass fish & live rock aquarium. I purchased a magnum 950 pump (following your advice -Steve) as my return pump. I tested the flow rate and this pump is pushing 540 gal/hr in my aquarium which I am very happy about (I collected the return water in a bucket and measured it out). After reading many posts regarding insufficient drain rates, I modified the All-Glass overflow kit to allow a 1.25" ID tube to drain into my sump. Needless to say my tank sounded like a flushing toilet and washing machine all in one. I was experiencing a huge siphon noise, a noisy waterfall effect in my overflow, and a very noise sump with lots of air bubbles. I also cannot increase the diameter of the drain hole or add another one because the bottom of the tank is tempered glass. After reading through hundreds of posts I came across someone who put a gate valve in the drain line and closed it just enough to exactly match the return pump's flow rate. I decided to duplicate this today (but with a ball valve for now) and the results have been terrific. The siphon noise is gone because the water level is far above the PVC drain pipe (I stopped using the all-glass float), the waterfall noise is gone because the overflow water level is only a few inches below the overflow lip, and the sump is very quiet because very little air is siphoned into the sump (also few air bubbles). I have read numerous times that you guys don't recommend any type of valve controlling the gravity overflow.
<Yes>
I don't understand this reasoning though, besides it being very difficult to exactly match the drain rate to the pump rate. Are there any other drawbacks by restricting the drain rate to match the pump rate that I can't think of?
<There is a possibility of clogging the valve and causing the water level in the tank to rise to the point that you have a flood.>
This seems to good to be true. I have been agonizing over my setup for 2 months now and desperately want to get the tank running. Your advice in the past and this website as a whole has been indispensable.
<I think you would be safer with a Durso-style overflow modification. See his webpage here http://www.rl180reef.com/>
Thanks, Jeff
<You are welcome. -Steven Pro>

Overflow Tube Size
Hi guys/gals- <<And hello to you...>>
I am looking for your guidance once again. I am setting up a 125 AGA salt tank & 2 corner overflows with fish and live rock. An upgrade from a 5yr old 55gal set up. <<Interesting, just moved my 54 into a 180... have fun!>>
I have been told that the 1" bulkheads will move about 600gph each. If I stepped the 1" pipe up to a 1 1/4" right after it is connected to the overflow at the bottom of the tank, will this improve the flow rate at all? <<Not above and beyond what you can get through a 1" bulkhead, but I think that is actually higher than 600gph - I think this specification may be that of the overflow.>> I would still have the 1" bulkheads but I thought the larger diameter would move more volume from that point on. <<The bulkhead is the limiting factor, even though it's not really limiting you.>>
I have a 2 magdrive12 pumps and am not sure if I need both or not. If I used both I think would need more overflow than the 1" bulkheads can provide. correct? <<Well, I think this pump is rated at something like 900-ish at a 4' head, and even this would be more than 600-gph per overflow. I'd try it when you do your leak test, and just plumb in valves on both pumps so you can dial them back a notch. More flow is always better if you can do it.>> 
I am keeping Tangs (Naso, Sailfin, regal blue and yellow) ,live rock and 2 Condy anemone, lots of snails/hermits. Plus an arrow crab. I have a 30 gal refugium and a 20 gal sump.
Do you think that my tank would benefit from the increased flow from two mag12 pumps? <<Oh yes.>> Could I use both pumps and close down the shut-off valve a little bit on both without damaging the pumps? <<Any restriction/valve placed on a pump should be done after the pump... if there is a valve in front of the pump, use this only to shut off the line and remove the pump for service.>>
I am not sure if this idea is nuts or not...... <<nuts... you mean like true-unions? These are excellent - use them everywhere you hard-plumb. Or do you mean the nuts on the bulkheads? If these make you nervous, smear some aquarium silicone on the gasket and put it together. It will be fine.>>
Could I tap off of a overflow line with a T and run some water into the refugium and have the overflow from the refugium tap back into the same overflow line farther down line? No pumps involved. Both T's would be before the sump. <<You could - might be best to try and arrange the refugium above the sump so that it could overflow into the sump. Is this what you were thinking?>>
The reason I ask is that I am hoping I can keep the refugium under the main tank on display but sump, pump, skimmer, etc.. would be on the other side of the wall in the room next door. <<Oh... sure. If you are taking the time to do a built-in with separate room, for certain.>>
Thanks and have a good weekend!!!
Den
<<You too. Cheers, J -- >>