Pool Nitrates Problems

Optimizing chemistry, improving circulation and dealing with nitrates!!!

When the water contains nitrates and the chemistry is out of balance, the likelihood of algae growth increases. Algae is always present, to some extent, waiting for the right opportunity.  There is no practical way to remove nitrates, from pool water.  However, you can do the next best thing, which is to remove the phosphates.  Water chemistry and proper sanitation are the first lines of defense.  A ColorQ, All-Digital Water Tester can perform all of the common pool water tests, eliminates the color-matching and guesswork.  There is a model, for every pool testing need.  Better Circulation helps make everything work more effectively.   The Circulator is a return jet replacement fitting, that improves filtration, eliminates the dead zones that promote algae growth, improves sanitizer distribution. Phosphates and Nitrates can increase the growth of algae and make treatment more difficult, as both are vital plant nutrients.  Nitrate removal is not practical, but phosphate removal is easy enough to do.  Adding Pool Refresh Total Trap will allow you to vacuum and filter out the phosphates and should make algae control more effective.

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Alternative Pool Water Sanitizers

When nitrates are a frequent problem, it is imperative to maintain proper sanitation.  Removing phosphates is a start, but adding some backup sanitizing is as important.  Chlorine levels rise and fall, based on pool usage and chemicals being added.  Most pools use some sort of chlorine.  A Salt Chlorine Generator is definitely a better way to do chlorine.  Salt chlorine generators are highly automated and give you better control.  In-Line and no-installation-required models are available.  Adding a Solar-Powered Pool Mineralizer introduces copper and zinc ions, that provide algae control and additional backup sanitizing.  This reduces the amount of chlorine required, to maintain an optimum level.  A Solar UV Sanitizer creates "free radicals" which help destroy algae and other microbes and provides some sanitizing backup.  It doesn't completely replace chlorine, but will provide better results and reduce chlorine usage.

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How to manage pools with high nitrate levels?

 Nitrates can promote the problem growth of algae in swimming pool water and can enter the water from such sources as: decaying plant matter, fertilizers, contaminated well water, acid rain, contamination with soil, ground water runoff, bird droppings, bather wastes, urine and sweat. Nitrate is a vital plant nutrient and the presence in swimming pool water, above 10-25 PPM, can cause accelerated algae growth in poorly maintained pools. Pools, that are properly maintained, usually do not have unexpected difficulty controlling algae, even in the presence of low levels of nitrates. Higher levels of nitrates can make algae control more difficult and increase the amount of chlorine required to maintain satisfactory control of algae.  The most practical and common method is water replacement. This is practical only if the new water is virtually nitrate free. The nest best thing to nitrate removal is phosphate removal. Both are vital plant nutrients and, depriving algae of phosphates, an make nitrates potentially less of a problem. Pool Refresh is one of the newest ways to eliminate phosphates, as well of problem minerals. Testing for nitrate is not common, but in those cases where algae control is proving difficult, despite apparently ideal pool water conditions, testing for nitrate and phosphate might be advantageous. If problems arise, refer to the Pool Problems Page, as a source of problem-solving information, broken down into various categories.  Scroll down the page and click on the linked keywords, catch phrases or images, in the archived answers below, to access additional information, on that topic or product.

► Questionable Nitrate Testing and Advice?

Hi, we have recently opened our pool. Have taken all the steps instructed to do including shock, Algaecide, alkalinity, pH decreaser. Pool had a greenish tent but clear. Had water tested and was instructed to add baking soda, more Algaecide and shock. Had water re tested and now we are being told we have a very high (off the chart) reading of nitrates in our pool. The place testing out water instructed us to add 6 lbs of shock every 24 hours until we can get a chlorine reading to hold for 24 hours on our test strip. Said it could take 3 weeks or longer and that the pool is seriously unsafe at this point and we should not even place a toe in the water. The pool is now clear and blue with Some algae present however nothing significant. However we are still getting no reading of chlorine on test strips after 2 days of treating. This amount of shock is costing us 75 dollars every 4 days. Does this sound accurate to you, and is there anything else we could or should do?  I have a lot of people saying the pool place is trying to rip us off, but we don't want to take any chances with our 9 year old or ourselves. Thank you in advance.

Rebecca D., 5/3/2018

Did they really say nitrates??? I sell lots of test equipment, much of it to dealers, and I almost never sell nitrate test strips. Ask to see their nitrate test kit.  Nitrates are a vital nutrient for algae and its presence can accelerate growth. The is NO practical chemical method of removing nitrates, from pool water, short of using a reverse osmosis water treatment apparatus and that might cost more that replacing the water. If you can't remove nitrates, you do the next best thing. You remove phosphates, which are also a vital nutrient for algae. This is doable and phosphate removal chemicals, such as Pool Refresh are available, for this purpose. There are no treatment chemicals for nitrates. NONE!  Nitrates up to 40 PPM are considered to be manageable. Ask to see the test results. If told it is too high to read, do this. Mix one part pool water with 9 parts of distilled water (from a supermarket) and ask for that to be tested. These results should be multiplied by 10.  Seriously unsafe sounds melodramatic. A pool should not be used, unless the chemistry is right and there are no signs of visible algae.  What he is doing suggests the problem is high combined chlorine. If there are still traces of algae, brush the walls down, add chlorine to raise the free chlorine to 5-10 PPM. Measure the total chlorine. If it reads more than 1 PPM higher than the free chlorine, you need to add more chlorine. The difference is combined chlorine and it is odorous and irritating. It takes 10 PPM of free chlorine to destroy 1 PPM of combined chlorine. To make the chlorine more effective, get the pH closer to 7.2. Don't drag this out. Test and add more chlorine, if needed, every few hours and keep the pump running 24/7, until the goal is reached.  Nitrates and phosphates make algae control more challenging, but not impossible, by any means,

Here are some things to consider. Replace the return jet fitting with The Pool Circulator. It will dramatically improve circulation, by creating a spiraling return flow. This helps eliminate the dead zones, that promote algae growth.  A solar-powered pool mineralizer will add another layer of algae protection, by releasing copper and zinc ions. This helps greatly, when the chlorine levels start to drop. It will reduce chlorine usage, as well.  How you add chlorine matters. A salt chlorine generator does it more consistently and on an automated basis. We have some no-installation required models, that you might consider.

I hope that this will be helpful. Please let me know how it turns out.

Sincerely.  Alan Schuster, 5/4/2018
 

► Nitrate Removal?

Hi Alan, I have read the archives about removing nitrates from pool water and the answer is removing a percentage of the water and refilling with clean water. On my research of the problem of Nitrate removal, I read the articles by the EPA on nitrate removal from sewage waste water. The process made use of methanol, ethanol, or acetic acid, as a carbon source, to convert the nitrates to nitrogen gas, which is then removed by aeration. Why wouldn't this work with nitrates in swimming pool water? Ethanol is obviously the safest choice but I don't know if the nitrogen gas will escape, from the surface, without additional aeration. Your comments please.

Terry M., 9/7/2017

You have a swimming pool and you are referencing nitrate removal on an industrial scale. There is no practical way to remove it from swimming pool water. If the level is under 40 PPM, it should be manageable. When you can't remove nitrates, you do the next best thing. You remove phosphates. Both are vital plant nutrients and eliminating phosphates makes nitrates less of a problem. Pool Refresh will remove nitrates and heavy metals, at the same time. Do you have access to low nitrate water? I hope that this is helpful.

Sincerely.  Alan Schuster, 9/7/2017


► Nitrates In Pool Water?

I've had some algae problems and have been told that it is due to nitrates in my pool water. Is that possible and what can I do about it? Thanks a lot.

Gloria B., 4/22/2014

Nitrates can certainly be a problem, especially above 10-25 PPM. They are a vital algae nutrient and literally act as fertilizer. If the nitrate level is low, you should be able to control the algae using standard shock, chlorine and algaecides.  The use of a phosphate eliminator, such as Pool REFRESH might be a good idea: it will help deprive algae of vital phosphate nutrients. Nitrates can come from a variety of sources: agriculturally contaminated well water, fertilizer, surface runoff contamination, sweat, urine, decaying plant matter, acid rain and wind blown debris. Trying to determine the source might help in controlling the problem.  It is possible to lower nitrate level with the use of iron-exchange resins, but is not really practical. The replacement, of all or part of the water, is the most common method to reduce nitrates.

Sincerely. Alan Schuster, 4/22/2014
 

► Ion-Exchange Resins Are Not Practical?

Dear Alan, in one of your replies about nitrate problems, you remarked that one can use ion exchange resins to remove nitrates. Where does one get them? I have called a dozen pool supply stores, and not only do they not sell them, they haven't even heard of them. I have also called resin manufactures: Ecowater, Siemens, and Culligan, and they don't market or install their systems for swimming pools. I would really appreciate any information about how to obtain these resins.  Thanks.

Marcelle D., 11/16/2013

Unfortunately ion exchange resins are not practical, which is why they are not available. There is no simple way to remove nitrates. Under 40 PPM should be manageable. Nitrates are a vital plant nutrient, as are phosphates. You may not be able to remove the nitrates, but you can remove the phosphates, which is the next best thing. Phosphates can be removed, by treating the pool water with Pool Refresh. I hope that this information will prove helpful.

Sincerely.  Alan Schuster, 11/16/2013


► Mistaken Notion?

Hi Alan! Thanks for taking the time to setup this website. I've found it very informative and answers a lot of the questions that I have as a pool owner.  A couple of questions:

1-The pool store where I take samples of my water have indicated that the reason I'm having problems with algae is the nitrate content in the water. I've tested it and it looks like it is in the 10 PPM range which based on the FAQ is within the acceptable range. Now the question, I have an 80,000 litre pool and they have indicated that I must put in 50 - 80 litres of liquid chlorine (shock) to get rid of the nitrate. Is this accurate? Should I be concerned about the nitrate level?

 2-Everybody seems to have a different answer to backwashing my sand filter. I usually backwash it when the pressure noticeably creeps higher than normal. I usually turn the filter on waste for 30 seconds, backwash for 2 minutes and then rinse for 30 seconds. Is this the correct backwashing procedure? Thanks.

Rick G., 9/18/2012

It is true that nitrates can add to the possibility of algae problems, but it is not inevitable. A 10 PPM level is not excessively high and should not be causing inevitable problems. The only way to lower the level would be to replace water and what is the nitrate level of the new water? Adding chlorine - no matter how much - will not lower the nitrates level one bit! Adding that amount of chlorine will have an effect on the algae, as well as your wallet. It is mistaken to think that chlorine, at any level will reduce nitrates. If you are having algae problems, pay more attention to the Free Chlorine level, pH and try using algaecide and/or a phosphate eliminator, such as POOL REFRESH. A level above 25 PPM is considered too high and should be lowered by water replacement. A somewhat dirty sand filter is more efficient that a sparkling clean filter. Backwash when the pressure rises too high and/or the water flow is too low. Backwashing unnecessarily or too often will reduce the effectiveness of the filter. To improve the efficiency of your sand filter you might consider replacing the sand, with a zeolite sand replacement filter media, the next time the sand need replacement. I hope that I have been helpful.

Sincerely. Alan Schuster, 9/18/2012

► Low Chlorine Readings?

I was just wondering if the free chlorine level would be low (.2) and the total chlorine level high (3.0) because we have traces of nitrates(12ppm) in our well water?  We started the season with good chlorine levels, but after we topped off the pool (and then it rained a LOT) the free chlorine level is very low.  The local pool store said to "triple shock" the pool, wait 3 hours, measure the free chlorine level and continue this process until we show free chlorine for 24 hours. We have already dumped 30 bags of shock into the pool and the free chlorine level is still non-existent! Please help! Thanks so much!

Kiki, 6/27/2012

Nitrates do not consume chlorine. A concentration of 12 PPM is manageable and should not present unusual problems. High is considered over 25 PPM. What nitrates do is stimulate algae growth by providing a necessary nutrient. In the presence of adequate Free Chlorine levels, the algae should be under control, even with low levels of nitrates. You have to add enough chlorine to boost the Free Chlorine level into the optimum range of 1-3 PPM. While you have added a considerable amount, the non-existent readings point to the fact that not enough has been added. Make sure that the chlorine test materials are working properly, by having another source confirm the readings. For free chlorine testing, I suggest using one of the ColorQ all-digital Water Analyzers, as they provide the right kind of information. To better assure proper overall pool water chemistry, visit a pool store that has a very reliable, professional lab such as a WaterLink SpinTouch Lab, rather than a less accurate test kit or strip reader.  I hope that I have been helpful.

Sincerely. Alan Schuster, 6/27/2012


► Nitrates - Phosphates Relationship?

I have a pool that is having problems with nitrates. My free chlorine level is 0.5 and I was told to add a phosphate eliminator to help reduce the nitrate level. I added 1 cup for the past 2 weeks and it hasn't made a dent in the nitrates and I shock my pool every week. Please help, any suggestions will be greatly appreciated. Thank you.

Tom, 5/30/2018

Someone is just a bit off the mark! Phosphate eliminators, such as POOL REFRESH, will not reduce the nitrate levels, just the phosphate levels. What you should have been told is that there is no practical way to eliminate the nitrates. Nitrates and phosphates are both vital plant (algae) nutrients. Being that you can't remove the nitrates, it becomes even more important to remove the phosphates. You're doing the right thing for the wrong reason. Have the water tested for phosphates and see how you're doing. I hope that this information proves helpful.

Sincerely. Alan Schuster, 5/31/2018


► Is It Toxic?

The level of nitrates in our pool is 25. Is that considered toxic? Do we have to drain our pool?

Chris D., 6/17/2006

At 25 PPM you at the limit. It is not a matter of toxicity. Nitrates can promote algae growth. Higher levels could lead to a constant battle. You can't keep nitrates from getting into the pool water from multiple sources. I would not do anything. If you reach a point that you are encountering difficulty controlling algae, I would replace part of the water in the pool. In the meantime, keep a good chlorine level, maintain the water chemistry and pool water clarity. You should  test for phosphates and treat, for that problem, with a product such as POOL REFRESH.  Removing phosphates will make the presence of nitrates less of a problem, as it removes a vital plant nutrient.  Enjoy the summer.

Sincerely. Alan Schuster, 6/1/2005


► Dealing With High Nitrates?

Your site is very informative and I have passed the link along to my friends. I have a 40 x 23' plaster pool. I had the water tested and they are telling me that I am off the charts on my reading for nitrates. I thought I heard a guy say over 80 but not sure. All I know is the test they did should have taken 5 minutes and mine was already way up at about 30 seconds. They are telling me to replace the water in the pool. Here is my question. If the algae are feeding on the nitrates shouldn't they be decreasing the nitrates in my pool? Should I let my pool go for a couple of days to allow the algae to dine on the nitrates and then do a partial replacement of the water in my pool? I have 24,000 gallons so I could take out and replace 18,000 gallons and then treat whatever algae is left with algaecide and shock. Does that make sense or am I way off the mark? I keep thinking about other replies you had on your site about how the algae like to dine on the nitrates and phosphates, so if I let them eat the nitrates and remove the phosphates shouldn't they eat themselves out of food and die on their own? I think I am simplifying this too much but that seems like it should work? Not sure how quickly they eat the nitrates though? I really don't want to pull the pressure plugs is what it comes down to so can I get away with a partial water change (3/4 of the water)? And would that 3/4 water change be enough to bring down the nitrates so that I can get my pool back to relative normalcy? Thanks for your time

Bob R., 5/19/2008

Interesting question! If you allow algae to grow and pump out algae and water, you will remove some of the phosphates and nitrates. If you use chlorine to destroy the algae, these minerals will merely be recycled. I am not sure how much the nitrates can be lowered by this desperate measure. A nitrate test should take 5 minutes maximum. If they did it sooner, the true answer could be higher. Ask for the actual number. This time mix one part of pool water with 9 parts of distilled water. Multiply their test result by 10, to get the true reading. I would also have the tap water tested. If you are going to replace any of the water, you need to know if the new water is actually going to make a difference. The nitrates just didn't happen overnight. While it is impractical to remove nitrates, if you remove the phosphates, you will diminish the effects of the nitrates. That is what I suggest you do. Get the phosphates down to 100 PPB, by adding a phosphate eliminator, such as POOL REFRESH, maintain the free chlorine at 2-4 PPM and keep the pH closer to 7.2. Just monitor the free chlorine carefully. I suggest using a test strip, or even better, one of the all-digital ColorQ water analyzers, as they provide the right kind of information. I hope that this information proves helpful.

Sincerely. Alan Schuster, 5/19/2008


► Low Nitrate Level?

I have a 38,000 gallon pool. The nitrate reading is 10ppm. I have been struggling to maintain a chlorine reading this season and recently started getting a bit of algae. The water looks amazing and the algae clears up with a touch of a 3" dichlor tablet. I am however dumping more chlorine and shock into the pool then ever before. My pool company suggests a partial drain and refill...do you agree? As it is the beginning of summer and my chorine demand has been low I am worried the problems will only get worse as we use the pool more and the temps rise. Thanks.

Linda H., 6/12/2012

Nitrates can be a problem. However, the concentration of nitrates has to be considered. Levels under 10 PPM are manageable. 10-25 bear some consideration of treatment. Over 25 PPM is a problem. Before doing anything, you should have the pool and replacement water tested. If present, there is no practical means to remove, other than water replacement. In place of removing nitrates, you should remove the phosphates, as this will deny the algae another vital nutrient and mitigate the presence of nitrates. Phosphates and any copper and iron, can be removed, by the addition of POOL REFRESH. If you opt to remove water, discuss this with the pool dealer or builder. Do it quickly and don't drag it out! I hope that this information will prove to be useful.

Sincerely. Alan Schuster, 6/12/2012


► Dealing With High Nitrate Levels?

I have a built in pool, 22,000 gallons. I opened it this spring, cleaned and shocked it. It tested high for combined chlorine, so I was told to shock again, 15 lbs. shock. Tested again, told to shock again, 20 lbs. of shock, also told at this point nitrates were at 52 ppm. We had a lot of rain, about 5" added to our pool. Took in another water sample, a different person did the testing this time, and said nitrates were at 47 (I guess the rain diluted them a bit) and not to bother putting any more shock in, that the pool needs to be drained. I was also told they cannot get accurate chlorine test readings when the nitrates are this high. This will be a huge expense, since he said our 9 year old liner will not survive the draining, and will also have to be replaced. I guess this is our only option? I had our well water tested at the pool store also, and it was high in nitrates, at 20 ppm. I am now waiting on a second test on our well water from another lab, and recommendations on that. My questions are: Are there any other options for us, besides draining the pool? And, while we are waiting to have this work done, is the water unsafe for my teenage kids to swim in? The pool looks beautifully clean and clear, it's hard to tell kids they can't go in it when it's 90 degrees outside! Help! Thanks.

Kathy R., 6/6/2006
 
It is not the end of the world and it is not a matter of safety. The presence of high nitrates (over 25 PPM) makes algae control a bit less forgiving. If you allow the free chlorine level to bottom out, it will grow sooner and faster. Therefore, keep better control of the free chlorine level and you should be OK. You can't remove nitrates, but you can dilute them down. Consider replacing 20% of the water every week for a few weeks. That will slowly drop the level.  While you can't remove nitrates, you can eliminate phosphates, by the addition of POOL REFRESH. This is another vital algae nutrient and removing it is the next best thing to removing nitrates. Deprived of phosphates, algae growth will be impeded. If the water is clear, there is no slime on the walls and the free chlorine is good, there is no reason not to enjoy the pool. Just monitor the free chlorine carefully. I suggest using a ColorQ All-Digital water Analyzer, which provides the right kind of information and eliminates all color-matching and guesswork. I hope that I have been helpful.

Sincerely. Alan Schuster, 6/7/2006


► Green Won't Leave?

My pool water tests perfect, time and time again. But still I am seeing periods of green water, even though I am adding lots of chlorine. The dealer has mentioned nitrates as a possible cause. Is this a possibility? Thanks for the reply.

Fred C., 8/11/2004

Nitrates are a distinct possibility. They act as fertilizer for the algae and can increase chlorine consumption.  If the pool water shows a nitrate concentration of more that 25 PPM, replacement of water might be a good idea. Knowing the probable source of the nitrates is important, in order to help avoid or minimize a recurrence. There is no chemical means of nitrate removal. Try removing the phosphates, using POOL REFRESH, which would be the next best option. I hope that I have been helpful. Good luck.

Sincerely. Alan Schuster, 8/11/2004


► Partial Refill Is Not Best Option?

We tried an open our pool a little early and have had a stormy spring. The result was I have just removed a ton of leaves in the attempt to reopen. I adjusted the alkalinity and pH to proper levels and used a polymer algaecide, along with 6 lbs of rapid shock just three days ago. The pool has turned from green to a cloudy blue. I have some remaining green on the walls. I tested the water today, and everything is right except for a 0 free chlorine reading and a minimal total chlorine reading. When the dealer tested the nitrates he said I was at 4.5 ppm and that I was wasting my money by adding any more chlorine or shock and that I would need to begin a series of waste water removal below the skimmer and refills that could take up to nine or ten cycles. I have begun this cycle this evening. Is this correct? I have a vinyl liner pool no bottom drain 30000 gallons.

Mike C., 5/24/2006

Levels under 10 PPM are considered manageable with proper chlorine levels. You might want to have the phosphate level tested. That you can do something about. Eliminating phosphates make nitrates less of a problem, because this other vital nutrient has been removed. POOL REFRESH can help you filter and/or vacuum out phosphates, as well as metal such as copper and iron.  I would not drain the water. It you follow his recommendation, you will never get it to zero. Probably not even below 2 PPM, even after 8-10 replacement of 10% each. I would work on getting a stable free chlorine level. You want some free chlorine to last through the night. Once done, there should be improvement in the water quality. By maintaining a consistent 1-3 PPM level of free chlorine, the nitrates should not present an insurmountable problem. For testing, I suggest a ColorQ all-digital water analyzer, which performs tests without color-matching of any sort.  Good luck and I hope that I have been helpful.

Sincerely. Alan Schuster, 5/24/2006


► Doesn't Add Up?

Dear Alan, I have been reading different things about nitrates, and I'm still not sure what to do. Our pool was tested a month and 1/2 ago for nitrates and phosphates and both tested over 1000 ppm. We tried a chemical to remove Phosphates and it still reads over 1000. Is the best thing to do to empty half the pool and refill it before we close the pool for the winter ? Do we also add a bunch of chorine to the 1/2 of the water that remains before we refill ? We have had no sign of algae in all this time, and only started putting more chlorine in the pool since we've known of the problem. It would be great to have your advice! Thanks.

Sue S., 9/5/2010

Something is not adding up! Are those numbers really Parts Per Million (PPM) and not Parts Per Billion (PPB)? With those phosphate and nitrate levels, you should be having major problems. Adding some phosphate remover, just won't reduce a level over 1000 PPM. If you pool is 10,000 gallons that means that there is more than 80 pounds of phosphates and 80 pounds of nitrates in the water. Adding a dose of a phosphate eliminator would barely make a dent. Unless your pool has been filled with water that has been agriculturally contaminated, I doubt that the levels could be that high. Replacing half the water would still leave the water unacceptable. What are the levels in the replacement water? I suggest that you have the pool water and tap water tested again. You might even want to have another dealer do the testing. If you are not having algae problems and not having difficulty maintaining an adequate level of Free Chlorine, you may not have a problem.  Winterizing the pool in the normal manner and revisiting the issue next spring, would be my recommendation, unless a retest proves otherwise. Replacement of water is the only remedy for nitrates. A level over 25 PPM is considered problematic. I hope that I have been helpful. Let me know what happens!

Sincerely, Alan Schuster, 9/5/2010

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