Re: nitrate, nitrite, hardness, alkalinity, pH of RO water?   11/14/06
Thanks for the quick reply. Looks like I have a larger problem with my grammar than I do with my RO unit!
<Heeee! But getting much better!>
When I test my RO water, what should the results look like? Should I see low PPM, low pH, low Alkalinity, etc...?
Chris-
<Low TDS (less than 10 ppm), a bit low pH (high sixes) going back to near neutral (7.0) over time, aeration, almost no alkalinity (less than 1 meq/l). You have searched, read on WWM re? Bob Fenner>

RO/DI not removing phosphate 11/25/05
Hi Guys, I am trying to figure out the origin of my problem. I recently purchased Pure-Flo II RO/DI Unit - 50 GPD TFC - 3 Canister and having troubles with it. So far I can only see that there is something wrong but I can't identify where exactly. So here what I have. Before attaching this unit to the water source I rinsed the carbon block for about 15 minutes under the stream of cold tap water in order to remove the trace of a phosphoric acid. 
After that I attached the unit to the water source. My tap water has Phosphates reading of 0.5 ppm. I discarded first 15 gallons of water and then produced additional 5 gallons to make a partial water change in my tank. After I did the water change, ~ 10% of my tank volume, next day I observed the boom of assorted algae. The phosphate and silicate readings in the tank are 0(I am using Salifert test kits). But how I was surprised when I observed that they are not zero in the RO/DI water that I made. In fact the level of phosphates is the same as the one in the tap water. 
Which made me think that the unit operates incorrectly or I am doing something wrong.  Thanks in Advance.  Alex  
<I would contact the company for support on this issue, but in brief... as you obviously know, carbon blocks often contain residual phosphoric acid.  I would suggest testing a sample of water that has passed through the carbon, but not through the RO or DI.  I suspect that you will find that the phosphates are off the chart.  Under normal circumstances, RO/DI will adequately reduce phosphate, but when such high concentrations are present coming in, some is going to make it through.  You will most likely have to replace the carbon blocks with pre-rinsed ones to solve this issue.>
Tank Info: 30G FOWLR, Remora Aqua C with MaxiJet, Lunarlite 2x65 PC/Actinic, MaxiJet 1200, Hagen power head 30, Fluval 204 (cleaned on daily basis), ~20 lb of LR, no fish no inverts but some kind of worms and insects that came probably with LR, still cycling. Water parameters: Ammonia 0.25 (used to be 0 last Friday), Nitrite 0, Nitrate 5, Phosphate 0, Silicate 0, Ph. 8.3,  Calcium 400. 
<All sounds good!  Best Regards.  AdamC.>

RO/DI unit membrane change  - 5/8/2006
At which TDS reading should one change the membrane of a RO/DI unit?  I've had my unit for just over a year and my reading on my meter reads 75ppm IN, and 40ppm out.  I tried flushing out my membrane several times.  I'm thinking this is what is contributing to my Cyano problems.  I've eliminated all other reasons Cyano.  What do you guys think?
Nilesh
<Nilesh - Assuming your TDS meter works fine, most people strive for an output of 0-3ppm.  Thus, 40ppm is quite high.  After 6 months to 1 year, many manufacturers recommend changing all the filters/membranes.  However, it really depends on the system, overall use, and your water supply.  If you had been testing with the TDS meter since the beginning, you could have seen the water level decline over time and be more certain that you need to change the filters/membranes.  At this point, I would suggest making sure the TDS meter is working properly by checking it with distilled water (it should be close to 0ppm).  If it is, contact the RO/DI manufacturer and see what they recommend you replace.  My guess is that without being able to test each component individually, they are going to recommend replacing all of the filters/membranes.  If so, then you can test the output with your TDS meter and develop a baseline to monitor over time.  Due to variations in water supply and plumbing, everyone's input and output TDS readings are different.  However, the input TDS should remain relatively constant for you over the course of the year.  Once you know your individual situation, you'll be able to figure out how often to change the components going forward.  Best of luck, Roy>

RO System Output...Possibly Damaged or Faulty Membranes - 09/27/06
I am having a problem with my RO system.
<<Oh?>>
I have a Kent 200gpd system with an add-on DI.
<<Big system>>
I store all in a 200G plastic tank.  After replacing all the cartridges (including membranes) it will run great with the TDS reading 0.
<<Good...>>
But within about a month I notice that the RO unit is producing water much faster than usual (it normally produce about 125-150gpd) and the TDS is up to about 140 which is about the same as tap water.
<<Mmm...not so good...>>
I change the sediment and carbon prefilter about every 7-10 days, because I read you should change them every two to three thousand gallons.
<<And you produce that much filtered water in a week?...wow>>
It seems as if the membranes are failing.
<<Indeed...am in agreement>>
Any help would be appreciated.
<<A couple things come to mind...Firstly, I would try a different source for obtaining membranes.  Next, make sure you are getting 'TFC' membranes as opposed to 'CTA' membranes.  The CTA membranes break down very quickly if exposed to chlorine, and if your carbon prefilter is not adequate at removing this, well...  Also, rather than using the sediment prefilter, consider using "micron rated" solid carbon blocks.  Using a 5-micron block as your first-stage and a 1-micron block as your second-stage will still filter out particulates while providing some additional chemical prefiltering of the water before it reaches the membrane.  Most carbon block combinations such as this will usually give you in excess of 5,000 gallons usage, and I seem to recall some with 30,000 gallon usage ratings (these blocks can also be easily rinsed of loose sediment on a weekly/monthly basis)>>
Thanks, Daniel
<<Hope this proves helpful.  Regards, EricR>>

How to recharge a deionizer
I've looked and looked but haven't found anyone who will lay out step by step how to recharge a deionizer. I know you first have to have one that is rechargeable. any help?
thanks Brian
<Mmmm, well... some resins are recharged with caustic substances... some with salts... Some can't be economically recharged by simple soaking (require high pressure, temperature in the process). My real advice is to contact the manufacturer or barring this, find out the name of the ion-exchange resins in your unit and search the Net, reference works in a large (college) library re this issue. Bob Fenner>

- RO Filter Changes, and More -
Hi there how are you, I have a couple of questions. <I am well... I will try my best to answer your questions.>
how do I know when it is time to replace the filters on a RO unit, I have the Coralife unit with a 1 micron filter, carbon. sediment filter. <There are no hard-set rules, but six months for the micron filter is pretty good - if you change this filter often you can extend the life of the other cartridges. Typically the micron filter is the cheapest in the bunch.>
I was told that when the output slows down that you need to replace the filters, my question is do you only replace some of the filters or all of them? <I personally don't wait that long, and my RO unit has clear filter cartridges so it's possible to see when the micron cartridge is getting loaded up with particulates. I've moved a lot in the past year and a half and have found that the mileage on these filters varies greatly.> or is there a better way of knowing when to replace the filters, they are rather expensive so I would like to be sure. <Well, for certain they don't last forever so... you just need to keep an eye on things.> Can you test the water coming out of the RO unit, like if the hardness goes up is this a sign or can you recommend me the best way to know when to replace the filters, also I only use 15 to 20 gallons a week so I shut off the RO unit when not in use, I was told that's its not good for the filter if it is shut off, is this true? <I've not heard this, can't verify it's truth but have shut my filter down many times, in fact right this minute it is doing nothing... think this is in fact pretty standard - as in I don't know anyone who's RO system is running 24/7.> I leave the hoses above the filter so the water does not drain out. <Sounds fine to me.>
If I don't need a lot of water why keep it going is this OK to do. <I wouldn't be too worried about it.> I would like to store some of it also. If I used Rubbermaid containers say a couple of 20 gallons how long could I store it for with no air stones or powerheads, or this not a good idea. <It's not good to store water without some form of circulation... it will go stale relatively quickly.>
my other question is about the PolyFilter by bio marine, good product, but when do I know when it is time to change it the instructions say you can wash it and reuse it, but I thought I read somewhere on your site that they cant be re-used, also since it is a little expensive how often would you recommend using it. <The Polyfilter is supposed to change colors as it absorbs undesirable chemical compounds. I wouldn't run one of these all the time if cost is an issue - instead just use normal filter pads if all you need is physical filtration. A Polyfilter is both physical and chemical filtration.> my parameters are pretty good, would I still use it even if everything is Ok, or only when I have high ammonia readings, also does the PolyFilter remove trace elements or just the bad stuff, I heard that it wont remove elements out of the salt but will remove any supplements I add to my tank. <It will remove some but not all... but if you're dealing with high ammonia issues, I wouldn't be using a Polyfilter but instead attack the problems at the source.>
thanks for your help in advance, your site has been very helpful.
Val
Toronto, Canada
<Cheers, J -- >

Update on Austin water
Hey, WWM-ites,
<Hello Glen!>
I went and got some RO water here in Austin yesterday, and ran my battery of tests against it.  The machine at the grocery store was showing that it had last been serviced on 11-6-04, and the store manager said it wasn't very heavily used.  Based on that limited info, I'm assuming that the media are still in good enough shape to reflect what would happen with an average RO system here.
<... not according to the results you post below... something is definitely awry>
As I expected, the pH wasn't any different from our tap water.  The RO water settled at pH 10.0
<What? If anything, a functional R.O. device may show a drop in pH (below neutral)... Please see here: http://www.freedrinkingwater.com/water-education2/ro-ph.htm
Virtually all bicarbonate and carbonate is removed by reverse osmosis.>
on my meter, and a sample of tap water at the house registered pH 9.9.  kH and GH of the RO water registered zero with both the dip-strip and reagent tests, compared to the tap water's 3 dkH with reagent and <75 ppm kH and ~80 ppm GH with the dip strip.  Temperature of both samples was 71F.
<This is about right where it should be...>
Also, for what it's worth (if it's salient to the total osmotic pressure discussion) the City reports TDS at average 184 ppm in September (the last reported month) and for the third quarter of '04.
<Okay>
Interesting results - RO here has all the "stuff" removed from it, but still has to be treated fairly aggressively to bring the pH down to neutral, and then buffered to stabilize it (right?).
<... should not have to be treated for pH at all... I would check your testing gear (against standards, use other means...)... aerating it should register a near neutral pH over an hours time or so. Does indeed have to have alkaline material added to re-buffer.>
Thanks again for having such a fantastic trove of info for those of us who are a bit less informed!
Glen

Re: Update on Austin water
Not to be argumentative, but 'cuz I truly want to understand...
<Me too>
I calibrated my pH meter to a 7.01 and 5.01 standard a week and a half ago, and the tank readings have been holding pretty steady (up 0.11 - the tank is just slightly into its cycle - ammonia reading ~0.5, nitrites and nitrates still 0).  The City reports an average total alkalinity at the tap of 60, and a total hardness of 86, which are in line with my not-very-sensitive test kits.  Doesn't this indicate that there isn't much carbonate or bicarbonate to begin with?
<Depends on relative measures, what you call "not much"... this is considerable if it is coming out of an R.O. unit, about so-so for U.S. tapwater... and very hard for general Amazonian comparison...>
I called our LFS a minute ago, and was told that their RO pH is nearly identical (a couple of tenths lower) to their tap water, at 9.2-9.4 (they draw from a different aquifer, and the slightly lower pH is in line with the City's reports).
<Strange... or maybe I should state, unfamiliar to me... our R.O. water has a pH of nearly 7.0, with the source water (San Diego) at 8.2-8.4 most days>
I know that y'all's water treatment FAQ says that aeration would raise a slightly acidic pH out of a RO system to neutral, by neutralizing the carbonic acid - will it also drop a pH three points?
<Not easily... depending on what (carbonate likely at this high a pH) is elevating the pH, and if there is any alkaline reserve (buffer aka) at this high pH...>
If not, does the approach I asked about in yesterday's question (titled "Plan of attack for very soft, very basic tap water") make sense?
<Am copying and pasting a pertinent part of this here:
"Here's my approach to the water.  Please let me know if there's something I should do differently:
1.  20% water changes once a week, with substrate vacuuming.
2.  Dechloraminate 20-25 gallons at a time (in a dedicated new trash can) - easier and more uniform to treat a bunch all at once.
3.  Bring the pH down to 7.0 (using the sodium biphosphate product (anything better?)).
4.  Boost the kH and GH into more the 125 ppm range using calcium carbonate.  (Would something else, or a different value, be better?  If we actually adhere to this rate of water replacement, does our tap water need additional buffering, or is the little bit that's there going to be enough?)
5.  Aerate and tweak temperature overnight before a water change.
6.  Judicious chemistry monitoring between changes.
Since RO water still needs to be tweaked with pH adjustment, buffer, and essential minerals - why not adjust the tap water?  Also, I bet the pH of RO water around here is still quite high, given the tap water to start with - I'm going to get a gallon on the way home and test it.
Also, since the tap water is so soft to begin with, the double-whammy of a buffer and an acidic product shouldn't have too much impact on osmotic pressure, right?"
This does sound like a logical, workable plan... am still very curious as to what is "getting through" your Reverse Osmosis membrane that is resulting in such high pH though...>
I don't mind tweaking the water as necessary, but don't want to osmotically stress the fish.
Thanks again for your time,
Glen
<You are right to be concerned re osmotic shock... Do me/us a favor and call your water supplier (their phone number will be on the bill they mail you) and ask to speak with someone in water chemistry there. Please explain what you have here, and ask what they think is going on with your resultant pH. Bob Fenner>

Re: Austin water dept. chemist discussion
Well, that stumped 'em.
<Umm, me too... maybe we can start a club...>
I talked to the City's chemist, and he was surprised as well that the pH stays that high after reverse osmosis.  He said that the output of their deionization system (when they make their reagent-grade water) gives them a pH of 5.5 to 6 (as it's supposed to).
<Yes, agreed>
  He said he's not intimately familiar with how RO systems perform here, but he doesn't see any reason why the RO water still carries such a high pH.  His guess was that given the high concentration of hydroxyl ions, it's possible the RO system is being overwhelmed, and suggested that someone test the very first dribble out of a new RO cartridge to see if it reads closer to neutral.
<... hee heee... am given to suggest that your source water has a good deal of "hydroxyl" ion concentration... turns out that most brand X R.O. membranes allow ethanol/C2H5OH (and Glycol if interested) through... do you feel elated after a big glass of tap? Hey, maybe that's why it's called a "tap?". Just joshing here... and things change... I was a H.S.... Physics and Chemistry teacher years back... but OH's (Hydroxyls) are otherwise given the suffix "ol"... as in alcohol...>
The chemist also said they treat the water at the plant with calcium oxide to cut the sources' hardness from 185-200 down into the 85 range.  That explains why our tap water doesn't fit the usual high pH/hard water "norm" - it comes somewhat pre-softened.  From the reports, the source water is also around 170 ppm kH, where the tap is down around 60.
<Ahh, yes>
I called the LFS again and they said their RO water always has a pH above 9, though they've never tested it's initial output.  Another LFS backed up the tale - RO pH is never below 8.5, and almost always over 9.
<I believe you, them... am just at a loss to explain why/how this is happening. Hopefully some kindred chemistry soul will see our correspondence posted on WWM and chime in>
All the more reason to be religious about water changes, and not put in more additives than absolutely necessary, huh?  Thank goodness for a wife who's interested in aquariums, too!
<You lucky pug! Mine is kind enough to go and photograph on dive trips, even liveaboards, even though she is easily boat/motion sick>
Once again, thank you for your site and your input.  I really like your rational, cautious, livestock-oriented approach to the subject.
Glen
<Me too! Be chatting, Bob Fenner>

High Phosphate in RO water 8/12/05
Hello everyone, I'm a newbie to saltwater and I recently set up a 155 gallon reef tank.  In this time I've had trouble controlling my phosphate levels.  Here are my specs:
1.  155 gal tank
2.  Lightly stocked tank with 1 purple tang, 1 six line wrasse, 1 clown, 1 lawnmower blenny, 2 cleaner shrimps.
3.  2 mushrooms, 2 rocks of yellow polyps, 1 green star polyp.
4.  Two overflow boxes, aqua C ev-180 skimmer which produces lots of crap daily.  I use RO/DI water weekly and perform a 10 % water change every week. My RO system is from Coralife-pure-flo.
4.All water parameters are normal except the phosphate level which is a whopping 1 ppm with the Salifert test!
I thought for the last three months that the levels were high because I was feeding too much but I wasn't.  Sometimes I would actually skip a day so my fish could graze on the little hair algae I have in the tank.  I then thought that my test kit was wrong, so I bought a new Salifert test kit.  Anyways, I decided to test my RO/DI water without salt straight from the tube and the phosphate levels measured 1ppm!  I then checked my TAP water
from my faucet and it tested only 0.1 ppm.  I retested all my different waters and the results were the same.   I came to the conclusion that it seems like my unit is leaching out phosphate, is this possible?   The RO/DI unit is very new, I bought it 5 months ago and according to the instructions, the pre-filter needs to be changed in a months time and the membrane should last another 6 months.  So I still have time for change.  Any thoughts?  Nilesh <This is an easy one!  Activated carbon is made porous in the manufacturing process by exposing it to phosphoric acid.  If the carbon is not rinsed, it will leach phosphates in high concentration, much of which will pass through the RO membrane.  If you really want a shock, test the water coming directly out of the carbon block pre-filter!  The simplest option is to replace the pre-filters with good quality aquarium brand (something other than Coralife!).  Prefilters should be changed every six months to a year, but the membrane itself should last several years.  Best Regards.  AdamC.>

RO product water = 4.0 ppm P04!!!!!!!!!!!
Hey Guys!
I've been having some problems w/ phosphate levels the past 3 months.  I was reviewing your site today (awesome information, by the way) and realized that my problem may be the water source. <Ta da!> I bought a RO unit about the same time my problem started.  After testing the water from the unit, sure enough, the PO4 levels straight out of the unit are at 4 ppm! <Insert gagging face here>
I immediately went to an on-line aquatics supply store, they had a ton of replacement filters, but nothing specifically for PO4 removal.  I had no idea what to get.  So my question is twofold: 1) can I even buy a replacement RO filter that will remove phosphate, and 2) if so, do you know which one I should purchase?   I spent too much on that dang thing, not to be able to use it!  
<Are you sure you're using a reverse osmosis unit? With even the cheapest R/O unit you should have undetectable levels of phosphate in the product water. Your unit should have a sediment filter and carbon block before the membrane. It would also be a good idea to purchase a post deionizer for the product water of the RO. If you care to send me the specs of your unit, I'd be happy to make specific recommendations. -Kevin>
Your help would be greatly appreciated.
Mike

- 4ppm PO4 R/O water part 2 -
Dear Kevin,
Thanks for responding so quickly!  Yea, the unit I bought is definitely an RO.  Specifically, it's a 5-stage RO unit, the first cartridge is a sediment filter, followed by a pre-filter, a carbon filter,  the membrane next, and finally a "water polisher." <Hmmmm, I wonder what that is...> Other than this, I'm not really sure of the specs; it looks like any other RO I've seen.  It wasn't manufactured by a marine products company, e.g., Kent, et al., but I figured an RO is an RO, and so on. <Heh, don't worry, none of the marine products companies make any more than the stickers that they put on the units> I'm really at a loss as to why so much PO4 is coming through in this supposedly filtered water, and would like to get some filters to get it working right.  1/2 micron carbon filter perhaps?  I'm not sure. <I'd swap out the water polisher thing for a DI resin, any brand should fit.>
As a side note, last night after I wrote, I did a little experiment that you may be able to pass on.  I have a lot of water stored-up that I obviously can't use so I had to get the phosphate out.  I set up two 5 gallon buckets and filled them both with the RO water (this is water that's been through the unit, but still has a PO4 reading of 4).  From 9 p.m.- 9a.m. I ran a Whisper over-the-tank power filter filled w/ Polyfill on one bucket,  and put a submersible power filter that had a poly cartridge packed w/ Phosguard in the other.  This morning, the bucket w/ the over-the-tank/no Phosguard still read close to 4 ppm, while the submersible w/Phosguard read about .15 ppm. I know that's still high for a SW tank, but is certainly better than 4! <Yes, it's still very high, but 4 ppm makes me want to puke>
Regardless, I want to get my RO unit useable, without the extra Phosguard treatment. <Here's another experiment to do, remove the water polisher, make some water, and test it for phosphate. If it's still high, you need a new membrane. You can replace the polisher with a deionizer anytime, I'd do this right away. Good luck! -Kevin> Thanks for your advice, Mike

- More RO Phosphate -
Yea Kevin, that was a good idea to disconnect the "water polisher."  I took a water sample w/o it, and the PO4 was still at the same levels, but replacing it with a deionizer is the way to go.
<Mike, I wonder if it's your phosphate kit, although you did get a reasonable reading after running phosphate remover...>
One last idea, the carbon filter is only a few months old, but if they get saturated, they can release phosphates, right?
<No, but even so, the RO would take it all out.>
Maybe, it's the culprit.  Thanks for your help and suggestions; the WWM site as a whole is amazing.
<Alright, here's my thoughts on this whole phosphate saga: If the water coming out of your membrane is high in phosphates, there are only four possible reasons. 1) Your phosphate kit is wrong, but I don't believe that is the case... 2) Your membrane is bad, used up, finished, done 3) you're discarding the product water and using the rejected water 4) the phosphate fairy is coming at night and sprinkling it into your RO reservoir. This reminds me, time to change my DI resin! Good luck, -Kevin>

High PH from RO? (7/8/03)
I just purchased a new RO Unit... It is a Dolphin 100gpd unit from http://www.aquariumwaterfilters.com/RODI/Dolphin.html
I tested the water with the free TDS meter they give you and it tested out fine at 4ppm. However the pH on this water is at a whopping 9!!!!  Most RO water I've had experience with is at around 6.  <Wow!  That is strange, make sure your ph test is accurate, the liquid one get old and unreliable fast.  See if your LFS will test it for you to be sure its not just the test kit.   Also try testing your source water and see what that is.  Cody><<RO water is often of low pH due to the high/er solubility of ambient carbon dioxide (which goes into solution as carbonic acid mostly) and the lack of neutralizing alkalinity (these minerals have been removed by the RO process...). If the pH is high... something is amiss with your RO unit. RMF>>
Suggestions to why this is?
Thanks,
Sonny

-Recharging DI resin-
hello all and happy long weekend- <Thanks, alas, it's all gone now...> I was hoping you could help me with a few questions regarding a Kati/Ani 2 set-up I just purchased from Dr. Fosters. I also purchased replacement color changing resins from  Spectrapure for this same unit. I am now thinking this was a lack of knowledge induced mistake. I hope I can return them, they were a bit expensive. Now that I have the Kati/Ani units in my hand it looks like they are a sealed unit except for a little plug on the front. I am now thinking that you do not replace the resins inside and you just recharge them instead. Is this correct? <I just throw mine out when they're depleted. If you want to recharge them, check out http://www.reefs.org/library/article/twp_recharge.html>Or can they be replaced somehow also? <I'm sure there's a way to dump what's inside and replace with what you've bought. Check and see if that plug is removable.> From what I have read, it looks like I would use lye and Muriatic acid. Do the  resins just get rinsed/soaked in these chemicals and  reused again? <The chemicals should not be reused> Do you know if the recharged resins retain their color changing ability as they are exhausted ? <Yep, that's how you tell that they're in good shape (they'll be the original color)> I am guessing, yes. The instructions that came with the units are printed in somewhat of a broken English that makes me a bit unsure about the process. For hook-up ,the instructions talk about using Kati/Ani for" total desalting of water" and how to hook up the units. It shows tap water entering through the  center of the Kati unit, then flows over to the center of the Ani unit and then out for storage. Is this the correct procedure? <I'm not sure how this brand goes together but you want all water to go through the resin without any possible bypass> I do not know what desalting means. <Just means stripping the water of all impurities> I apologize for all of the newbie questions regarding DI water but I do not want to make a mistake and hurt any of my longtime finned friends. <I hear ya, better safe than sorry!> Have a nice weekend and thank you for your time <Good luck! -Kevin>  Dennis

- RO/DI Water Smell? -
Hi,
<Hello, JasonC here...>
I have read all the topics about my problem in the section, but I did not find anything similar to my problem.
I appreciate if you could give me some advise about this. Here is the problem:
I have new Kent Marine RO/DI HIS 60, and it has made only 140 gallons of water for 10 days till now. I have disconnect the unit from the water supply for a 1-2 days and after that, when I connect it again I have noticed that water has some smell, I check for nitrate, phosphate and ammonia and there is none. I have used some of this water in my knew tank and now I'm a little afraid of what might happen. <Because some water stays in the filter, it is possible for the water to become stale and if prevailing conditions are right [heat, light, etc.] you can even begin to grow things in the filters. This is probably what happened in your case. I would first try putting some of this water into a bucket or garbage can and aerate it vigorously... see if the smell goes away. If that doesn't seem to help, I would try running 10 to 20 gallons to waste and see if the smell goes away. If not, you may need to disassemble the three cartridge filters, bleach them and replace the cartridges.><<May need to bleach/sterilize the cartridges... to eliminate microbes here. RMF>>
I appreciate your help in advanced
<If you plan to let this unit sit for any time, you should take it apart.>
Regards
<Cheers, J -- >

- RO/DI Water Smell? Follow-up -
Uhhh... that is a quick reply. Thank you. After aerating heavily I can hard noticed that smell.
What are you suggesting to me, can I use that water or not? <I think so, sure.> The unit now creates a water with no smell, but the first block cartridge is, let me say black, not dirty. <Replace it.> Is  possible that I must change it after 130 gallons of make up water. <Perhaps your source water is just really bad, so yes... it is possible that after 130 gallons that filter must be replaced.>
Thanks again
<Cheers, J -- >

- Odd RO Results -
Got a strange water question, I looked around the site and have not seen a match. <Ok.> So, here goes..  The water coming out of my RO has a very high Ph reading like 8.4, thought this should be more like 7.0? <Something like that.> I have re-calibrated my Pin Point Ph monitor and get the same reading.  This Ph reading does not seem to change with aeration over 48 hours. <Interesting.> If the Ph is 8.4 should I still add buffer before mixing in the salt?  I have used my La Motte hardness test kit and the dKH is like 4. <It probably wouldn't hurt to buffer this water a little bit - shouldn't need to worry about the pH.> What gives? <Perhaps something is wrong, perhaps something in one of the cartridges, hard to know exactly but would move through a process of elimination to try and find out. Would start with testing your source water.> Brian
<Cheers, J -- >

Kati Ani deionizer units 11/11/03
Hope all are well?
<and you in kind, my friend>
Anthony which of the Kati Ani unit did you buy & where can I find more info about them besides stern & foster also do you know who may sale them wholesale.    
<I have favored the "Kati Ani" brand for many years and purchased mine wholesale from a regional distributor in Maryland: Peter Thode at Gwynnbrook Farms - an old German discus breeder. I hope he is still around and in business (his son(s) were involved too). Nice folks>
what does it cost to recharge units .
<mere pennies per gallon with Muriatic acid and lye>
One of your many friends in fish      ROCKY
<kind regards, Anthony>            

Questions about R/O water and mixing salt 12/15/03
I have some questions about R/O water and mixing salt that I was hoping you could answer (I couldn't find the exact answers on your site):
- How many PPM of TDS solids are acceptable in R/o water before the R/O membrane needs replacing?  5 PPM, 20 PPM, ???  
<somewhere between the two in my opinion. I favor changing it by 10ppm>
Is TDS and ppm the right thing to be checking to determine when the R/o membrane needs to be replaced?
<good question. It depends on your use of the water. If you are using RO because you are breeding discus fishes, then TDS is a big deal (less is better here). But if your RO is for marines, many of the hardness minerals are actually desirable and we are instead using RO to rid nutrients/contaminants (metals, phosphate, etc). As such, you will want to test for things other than TDS>
- I've noticed that my salt mixing tank will build up a brownish residue over months on the sides and on the aeration stones, heater.   
<may simply be a bacterial slime. Your vat is hardly sterile, and as such growths will develop in time>
I use Rubbermaid tubs for my R/O tanks and salt mixing tank.  the r/o tanks never get this residue, but the salt tanks do, and the only thing different in the salt tank is that it is aerated, heated with a titanium heater, and has salt (instant ocean).  Any ideas on what causes the brown residue slim?   Is it harmful?  It looks almost like a rust, but comes off easily via wiping.
<not harmful at all... if the vessel gets any indirect room light, the growth may also be diatoms>    
- Your site indicates that when mixing salt, you should:  1) get r/o water, 2) aerate it and heat it  3) add buffer to increase alk, and then 4) add salt.   How much buffer should be added - enough to reach normal salt water alk?
<yes... obey your test kit on this one. It will vary depending on the quality of RO water being produced>
-lastly, I found a faq on your site that indicated saltwater plants (Caulerpa) could go thru a freshwater dip prior to quarantine (like fish).  
<some will, but many wont>
How long should the dip last - and is this only for Caulerpa, or can most macro algae tolerate this (like Halimeda)?
<very few will survive the osmotic shock of FW. Its best instead to simply quarantine all as you do your fish in a separate QT tank for 3-4 weeks before moving into the main display>
thanks!<best regards, Anthony>

Questions about R/O water and mixing salt IV 12/22/03
Thanks for your reply, but I'm still a little confused about a couple of your answers:
c) Is it correct to assume that TDS meters measure all dissolved solids (if there are 3ppm of phosphate in water, then the TDS must be at or above 3ppm)?
> <I'm not sure that I understand the angle/intent of your question here? Especially in light of a marine aquarium with several hundred ppm of TDS>
I'm talking strictly about R/O water.  If the TDS meter reads 5 ppm in the R/O water, does that mean that any phosphate that might be in the R/O water would have to be less than or equal to 5ppm (does the TDS meter include phosphates in its ppm reading?).  If so, does the TDS meter include just inorganic phosphates or organic as well.
<ahhh... I see. And frankly am not completely certain that I know the answer although I suspect that at least some phosphate (organic) is not reflected in this measure of solids. The correct answer though depends on the membrane (what they will or won't admit/pass). A call or look at the mfg specs will answer this question clearly mate>
Also, you've indicated that you'd change r/o membranes for r/o water used in reef tanks if the water reached 5-10 ppm. because of this, I'm assuming those Kent r/o water TDS meters (black box) aren't useful because their most sensitive setting is 50 ppm.  Is this correct?
<Frankly... I don't use RO units (they waste obscene amounts of water... I prefer DI). And as a consumer, I do not hold most Kent products in high regard>
You mentioned using lux/par meters to get an objective assessment of the 'quality' of light being produced by bulbs.  Can you recommend specific brands of quality PAR meters (and lux meters)?   
<yes... "Apogee" brand PAR meters are popular with aquarists. A wide range of price and quality is available too>
I've used lux meters in the past, but they seem to be very sensitive/inaccurate (a small change in angle - <10 DEGREES - Can often double the reading).   Thanks!
The reason I'm asking these questions is I've had 2 75 gallon reef tanks running for a couple of years without problems.  Over the past couple of months, both tanks have had similar problems:  overgrowth with a Cyanobacteria-like algae that covers/suffocates the coralline algae.  
<many possible reasons for this>
It is not like Cyanobacteria in that it is like tar - almost impossible to remove even with brushes.  Fish seem fine, but all snails/crabs and corals have died (mushrooms, SPS, LPS, etc).  I've checked/rechecked water quality, and everything seems fine:  ammonia=0, nitrite/nitrate=0, calcium=400+, alk=8-10, ph=7.9-8.3.  
<the pH is way too low in my opinion... 8.3-8.6 is closer to NSW and regardless is known to inhibit many nuisance algae. 7.9-8.3 is also too wild of a swing between day and night (aeration deficiencies?)>
Phosphates/silicates read 0 (SeaChem test kits).  I'm at a loss to explain, but since it affected both tanks, I thought it could have been the pc bulbs (only 4 months old when this started) and have changed them w/o results.  Also thought it might be my R/o water - but TDS meters (multiple) show it at 5 ppm.  I've done massive multiple water changes - 40% - without any change in rate of this dang Cyanobacteria like growth.  I've put in poly filters and SeaChem's PhosGuard w/o change (do these filter medias absorb only inorganic phosphate or both organic/inorganic) Any ideas?  
<inadequate water flow is commonly a catalyst (needing 10-20X minimum... and be sure to clean those pumps and powerheads with acid/vinegar every 4-5 months to achieve max water flow)>
Thanks  - from a coral reef fan who thought he knew what he was doing for a couple of years only to be demoralized by this latest setback.  
<no worries... can be easily corrected in time. Anthony>

- Lifespan of Deionization Cartridges -
I'm considering purchasing a Kent Maxxima system. I can find lots of info on how frequently to change the various filters, except for the deionization resin filter. I can't find any info on how frequently these need to be changed. Do you know?
<The 'amount' of time is a range, depending on the quality of the source water. Most DI cartridges change color as the resin in them is used up. That's the best way to know when to swap it out.
Cheers, J -- >

- Odd RO Testing Results -
Hi Bob, Anthony, et al....
I just got a new RO/DI unit very recently as I know my tap water has some issues. One issue is called mix it with salt, and it turns blue after it clouds to no end in a white bucket. <Something seems very wrong about that... what brand of salt is this?> The other issue is I suspect it has been a major contributor of phosphates in my tanks (fresh and salt).
I flushed the unit for a few hours, and the pH coming out of the unit is higher than what goes in it. At first I was getting a reading of 10+ and I can't get anything better than either 8.5-9.0 after flushing for a few hours. <Wouldn't expect the pH to be much higher, should be in the range of about 7.0 - neutral after water has been filtered with RO.> After talking to fellow hobbyists with the same brand of unit or a unit in general we came to a few scenarios. One was called I screwed up my lines from the membrane, one was the manufacturer suggests a break in period, and the other is called the test kit won't work. <Or all three.> Someone else bought the same exact unit from the same exact person and tested the pH with a liquid freshwater kit, and got the same results.
I did test the GH and KH of the water, and I don't get any color at all when adding drops to the water, so there is nothing that is readily jumping out at me that says this water has anything in it that would raise the pH. I don't have a TDS meter though I wish I had one. The manufacturer says this sounds like a break in issue, and just keep flushing the membrane. We have ruled out plumbing errors.
I have read that testing pH for DI water is a real pain, and even with a digital meter it can be a pain as one can contaminate the probes, or CO2 in the air can throw it off. <Not that much - you should be able to test quite close to the actual number... CO2 and other contaminants should throw things off very little. Can let the probe sit in distilled water if you are concerned about the same.> If I have flushed the membrane for a few hours, and there is no sign of anything that would buffer that water, or otherwise raise the pH, do you see any way that the pH could actually be that high? <Hmm... my RO/DI break-in was supposed to be 100 gallons... would have taken several days to break in, not just a couple of hours.> I have tested the rejection water of the membrane and it yields the same results. However, the water is much clearer (I have a time seeing it in a container at times its so clear), and there is absolutely no smell of chlorine at all.
I read 1 case on one of the FAQ pages for RO units in which a woman had a like problem and her litmus strips gave a more accurate result supposedly. I am inclined to say the test kit just will not work for DI water. However, I am not 100% sure of this. Any opinion would be appreciated. <Hmm... is why I don't use test 'kits' for pH - digital probes are more reliable, quick, etc. I'm not color blind but I also just can't tell subtle changes in purple to get an accurate pH reading.>
Thank You,
Joseph
<Cheers, J -- >

Re: Hair Algae (time to check that chemical cartridge)
I tested the output from my r/o unit and the phosphate reading was 0.2 which is the same reading I'm getting out of my tank and the tap. I suspect the test kit and am buying another tonight to verify. Question is will the Euro-Reef remove phosphates from the water? I just installed it and I'm getting real good production from this skimmer. Should I reduce the photo-period? Will this hurt anything? I've already used a phosphate sponge! David
<If the test kit is correct, then your RO needs help or a DI unit to follow. Your skimmer will remove dissolved organics, but likely not phosphates. Water changes, water changes, water changes (with phosphate free water). Leave all as is except possibly source water, nutrient export with water changes. Once this is under control the hair algae is history.  Best of luck!  Craig>

RO/DI Unit Filter Interchange
Excellent resource for the aquarium enthusiast!
<I speak for the crew in thanking you!>
Just a quick question about RO/DI systems.  I have a Kent Marine Maxxima Hi-S 35 RO/DI unit.  I need to replace the sediment filter, carbon filter, resin cartridge, and membrane in my unit.  I've heard positives comments about the Spectrapure systems.  So I'm considering replacing those 4 filtering components with the Spectrapure brand.  Will SpectraPure fit in my unit and is this a good idea?
Thanks for the assistance, Edmond    
<The only question would be the membrane, but these cartridges, filters etc. are all fairly standard as are most RO housings/membranes. Just ask Spectrapure or where ever you are purchasing replacements, they should be able to help. Make sure you match the flow restrictor with the membrane.  Craig>

Rechargeable De-Ionizers
I just purchased a Kent Deion 200R, to replace the tap water filter that I have been using.  I bought this unit because they state that the media can be regenerated.  However, they don't tell how!  You have to use Muriatic acid, and lye!  Sounds dangerous to me.
<Depends on your abilities and of course, desire to do so. You sound like an RO/DI candidate to me.>
So, my question is, should I just send the unit back, or do you know of a business (Culligan?) that would regenerate this stuff for me.
<You might check SpectraPure or even Kent. There are folks on the WetWebForums that have done this, perhaps check there.>
Right now I feel like I have just paid 200 dollars for a large version of the tap water filter that I have been using.
<More or less that's what you did. It sounds like you should return the unit before you use it and research a good RO unit for your water conditions, perhaps with a DI unit following the RO to remove any additional elements (silicates, etc.).>
I probably could do the process of regenerating the media myself, but what do I do with the waste?
<Call your county land fill and see if they have a facility for Muriatic acid, lye, etc.>
I don't think that I want to put acid into my septic, and I don't think that I want to dump it down the curb, either.
<Thank you for being a good citizen! The landfill or county/city will have a facility for this waste.>
Thanks again for a great web site, I have used huge amounts of information from your FAQ's. Mike
<Thanks Mike, hope this helps!  Craig>

Choosing RO/DI - Chlorine vs. Chloramine
Hello & Good Day,
Everyday reader of your Daily FAQ.  I don't really have a question per se, just wanting to pass along some information for people researching the various RO or RO/DI units for purchase.
<Okay>
Once you've decided on the Make/Model of the unit for you and your fishes and prior to placing the order, call your local Public Works and ask a simple question;
Are you using Chlorine or Chloramines for water purification?
<Almost all United States municipalities use chloramine>
Knowing the answer, and passing this information along to your vendor of choice will ensure you get the proper Carbon Filtering Media.
Case in Point - I purchased a 4-Stage RO/DI unit from Aquatic Reefs back in February. Not knowing the answer to the Chlorine/Chloramine question, not knowing there was a difference and not being told beforehand of the importance of the difference I placed my order. Unit arrived and I, excited as a kid at Christmas hooked it up and proceeded to make RO/DI unit water for my tank.
Fast-forward to Apr 16th. RO/DI water now measures 45+ TDS. I think to myself -Wow- I've only put approx 125gals through this rig and I already need to replace a filter. So I call Aquatic Reefs.
Troubleshooting the now high output and short lifespan of the filtering media led to the realization that my local Public Works is using Chloramine for purification. My original setup was shipped with Filter Media for stripping out Chlorine. The Chloramine has basically 'cooked' the Filter Media, greatly reducing its lifespan.
So, in closing, take the extra few minutes to research if you'll need the Filter Media for stripping Chlorine or for stripping Chloramine.
Then, be sure to pass the info along to the vendor.
I hope this little bit of info is able to help someone out. I'd also like to do a quick shout-out to John at Aquatic Reef Systems. Both he and the company continue to earn High Marks!
Many Thanks,
Scott
<Thank you for sending this along. Bob Fenner>

Water Pressure Issues with New RO/DI Unit
Hey folks,
I purchased a Coralife 50 GPD RO/DI unit yesterday and am wondering about the pressure of water that enters it. I've hooked up the unit to my No Spill 50 foot water tube which is attached to the faucet in the garage.. I'm finding that the amount of purified water exiting is very little. To quantify it, it's like leaving a faucet open slightly. I'm not sure if it's because I've hooked it up to the No Spill, or is it the water pressure (which seems very strong when I use my garden hose!). The instructions also mentioned that low water temperature can reduce flow. Any thoughts? 
<Mmm... there's bound to be some pressure loss due to head pressure/resistance here... but not much... You could (while you're about) try measuring the actual production per unit time (with a container of known volume, time piece...). Likely you're getting about what the unit is made for.... about two gallons an hour... Bob Fenner>

Re: RO/DI volume testing
Thanks Bob,
I'm going to try the unit straight from the faucet and see if it makes a difference!
Nilesh
<Real good. Bob Fenner> 

Ro/di
I am installing a new ro/di unit! And I am going to use it for metal plating, so I am going to be using a 40 gallon storage tank! I have been searching everywhere to find the answer to my question, and I have yet to find it, so hopefully you can help me out. If the ro/di unit has to have 35 PSI to operate correctly, then does this mean that I could mount my ro/di unit lower then the tank for easy filter changes, or will the unit have to be higher then the tank in order for gravity to flow the water into the tank, and the auto shut off work properly?
<The auto-shut off isn't important as the pressure on the supply side is/will be higher... I would definitely install good shut-off valves (they sell these at Lowe's and Home Depot made of brass for reasonable) ahead and after the unit to facilitate taking it apart>
I have heard that these units create a lot of waste water, about 4 to 1. 
<This is about right... but in actuality... considering the amount of water folks toss on their lawns, landscape, leaks down the toilet... this is miniscule (not just IMO, reality) esp. considering the pollution, time and trouble to go "buy bottle water at the store">
Could the water that is normally sent to the drain be rerouted back to filter through the system, or is the something in the water that will never be removed. Thanks, Wes
<I recycle ours to a my garden and have used such water for my fish ponds over many years... this water is barely more solute-laden... about 25% more per... at a flush rate of 4:1... Be chatting, Bob Fenner>

The Strangest Question That You Will Ever Have Concerning RO filters
Bob et. al.,
Here is an exceptionally strange question, I have an RO filter that I had sitting on the floor in my basement beside a drain (like an idiot I never mounted it). To make a long story short, the sewer line got backed up, black water (nothing gross or floating in it) came out of the drain and partially submersed the RO unit. Since these units are have water tight seals, is it safe to say that it is still safe to use and that there should be no risk of contamination by bacteria?
<I would think there would be little risk. As a precaution, I would flush out the unit, disposing of all the water and perhaps change the prefilters.>
I cleaned the floor with bleach, and heavily flushed the outside of the unit with running water. I guess in a worst case scenario, I could run a UV on the fresh water for a couple of days before use.
<You could do that, if you have an extra unit laying around, preferably not in sewage, too.>
Let me know what you think. As always, thanks, Tom
<Have a nice day! -Steven Pro>

Leaking solenoid
Hello all,
<< Looks like everyone else passed on this. >>
I've got a quick question about my RO filter.  I have a Kent Marine Maxxima set up for my top off.  The maxima is run to my sump with a float valve at the sump.  The solenoid is leaking from the middle.  The filter is about 5 years old and I seem to remember this happening once before.  I'm not sure what I did then, probably just tightened the screws and watched it for a while.  Before I did that again I thought it might be a good idea to find out the expected life of the solenoid and if they tend to leak like this.  << I would think the life is several years. >> Any thoughts, experience with this?  Thanks for your help and your great site! << Sorry we can't be of more assistance.  I'd feel bad recommending any action other than contacting the manufacture and telling them the scenario. >>
Larry  
<<  Blundell  >> <I'd replace this solenoid outright. RMF>

- Deionization for Chemophobics -
Dear Sir or Madam:
I am looking or a water purification system for a 75-gallon reef aquarium.  I like the fact that deionization (DI) units are less wasteful of water but I do not want to deal with the dangerous chemicals involved with recharging DI units.  I plan to simply replace the resins when they are depleted.
(1) For my situation, which is more advantageous:  mixed-bed systems or separate KATI/ANI-type systems? <Think perhaps this is six of one, half a dozen of the other as they say... either system would provide filtered water. Individual cartridges of single resin types will last longer than a single cartridge of mixed resin.>
(2) What type of prefiltration is required for DI units? <I would use both a particulate filter as well as a carbon filter - much like a two-stage RO unit without the RO. These prefilters will extend the life of the resin cartridges.>
Thanks very much.
Regards,
Paul.
<Cheers, J -- >

RO and DI unit malfunction?
I have just purchased a new 100GPD RO Filter for my discus, it is a six stage Reverse Osmosis & DI Filter.
The problem that I have, is it is not producing soft water, all readings are high, I might as well use my tap water.
<...?>
I ran it for 10 hours before testing the water, and I have tested the water from different stages to see if it is a certain section that is not working correctly.
I have now been advised from the supplier to rock it from side to side to remove any air trapped as this may also cause it to not clean the water correctly, but I can't see that that would make such a difference, can you help.
Thanks
Simon
<Something is awry here... may well be that the unit is still not "broken in"... I would give it another few days, flush, throw away the water... and keep testing. In the meanwhile, get out the directions for install and assure yourself you've connected the components correctly. Bob Fenner>

Mixed-Bed versus Rechargeable Deionization 1/11/05
I have two questions about deionization and determining what purification system is appropriate for my tap water.
(1) If rechargeability is not a factor, wouldn't mixed-bed deionization be more advantageous due to its ability to produce purer water?
<not necessarily true (usually not in fact). It depends wholly on the resin, and there are many kinds to be had. generally the rechargeable ones are better quality than the disposable hobby use satchels>
A representative of Kent Marine stated that a mixed bed deionizer will produce water with 18-megaohm resistivity compared to rechargeable deionizers that produce water with only 2-megaohm resistivity.  
<perhaps true of some low grade resin he was comparing to for marketing purposes. I assure you this is not the case for all others or even most rechargeables>
I notice that SpectraPure uses mixed-bed resins in its "Ultimate" DI system that is also capable of producing water with 18-megaohm resistivity.
<its indeed more profitable to keep selling disposable resin rather than rechargeable one time only ;))
Many chemophobics, such as myself, shy away from the caustic chemicals used to recharge resins and would simply replace depleted resins in any case.
<Yikes! What a waste of resources! And the recharge chemicals mix to form inert (literally drinkable as demonstrated by chem lab professionals with carefully measured molar concentrations). You are off the mark here my friend... wasting is not conscientious, re-using is IMO>
(2) Where can I take my tap water to be tested to determine if prefiltration & deionization alone is sufficient?
<many (water) testing labs online... do a google search for one that appeals to you (price. service, etc). Maybe ask your local water authority for their official analysis>
I'd like to forego wasteful reverse osmosis and use prefiltration with deionization if the quality of my tap water is good enough.  I live in Colorado and am deeply suspicious of my "Rocky Mountain spring water."  Don't ask me about Coors beer--I've smelled the water at the brewery. Regards, Paul.
<have no fear of the two column deionizers my friend... really efficient and environmentally friendly use/re-use. Anthony>

Googling for Dow RO membrane info.
Thank you for your assistance in the past. Can someone tell me what a Dow applied (tw30-1812-100) RO membrane is? Is it a TFC or CA or neither? Will this work for well water not having chlorine?
Chris Drialo
<Uhh, place the term "Dow applied (tw30-1812-100) RO membrane" in your search tool (I did in Google) and read on! Bob Fenner> 

Ruggedness of DI cartridge
As I usually do, in trying to better my 55 gallon SW set-up, I may have caused a problem. I just purchased a Kent Maxima Hi-S 60gpd RO/DI unit to help me deal with very "fertile" source water. The directions say for the first use to remove the DI cartridge for the first two hours of operation and then re-install it. I got excited last night when hooking it up and forgot to do this. The kicker is, the pressure from the unit caused my faucet to start to leak at the fittings 20 minutes into this initial set-up run so I had to stop it there. I stopped it because I live just north of Philadelphia and was in the middle of getting over a foot of snow and am sure it would have taken a few months of my fish budget for an emergency visit from a plumber! Then this morning, 11 hours later it hits me that I never removed the DI cartridge and that the cartridge sat for that time in the initial water that came through the system. I ran to my basement and removed the cartridge and let it drip dry but am now unclear what to do.
<Resume the break-in period as if you were just starting>
Do you think I ruined the cartridge?
<No>
I don't think the color of the cartridge changed but then if there was some type of chemical present in the membrane, it could have discolored the whole thing. Do you know the rationale for the removal of the DI as this would help decide if I need a new one?  Thanks, Amy
<The initial water from the rest of the unit has chemicals that are not easily "treated" by the deionization part... no big deal though. Bob Fenner> 

- Filtration Options -
I've got an extra R.O. filter setup (3-10 in. canisters + R.O. membrane). I was wondering whether I could use the three canister filters (i.e., bypass the R.O. membrane) and place them in the main pump return flow line in order to occasionally take advantage of micron-level filtration? Thanks.
<I would not do this unless you have an unlimited budget for replacing the filters. You'll find that placing them in the main return path will reduce your flow rate and clog the filters very quickly.
Cheers, J -- >