manage pools with higher 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 It is possible to remove nitrates by
placing packets of ion-exchange resins in the
skimmers, but 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
or images, in the archived answers below, to access additional information, on that topic or product.
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Problem-Solving Information, in a question and
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
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
Sincerely. Alan Schuster, 9/7/2015
► Nitrates In Pool
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
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.
If this website was helpful,
in solving your problem, please consider joining our
E-Letter Mailing List.
You'll receive 1-2 E-Letters a month, with helpful
information, new product updates, suggestions and sale
announcements. I hope that I have
provided the solution.
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.
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.
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
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
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
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
Sincerely. Alan Schuster, 9/18/2012
These's no practical solution for a Nitrate Problem.
However, Phosphate Removal can be the next best solution.
Nitrates are vital algae nutrients, as are
phosphates. You may not be able to remove the
nitrates, but you can remove the phosphates and
deprive algae of this vital nutrient. This is
the most practical solution.
Use a Phosphate Removal System to lower an existing
Consider using a salt chlorine generator, to help
assure continuous chlorination.
Improve circulation and eliminate dead zones . . . that promote algae
Monitor the phosphate level, so you can stay ahead
of the problem.
Use a 1-micron Pre-Filter to remove mineral-rich
sediments, from all additions of new water.
This unique, 2-part product removes phosphates, iron and other
Salt Chlorinators are a better, more effective way to
Circulator eliminates dead zones and improves sanitizer action.
a Phosphate Test Kit to monitor progress and alert you to a
a Pre-Filter to remove mineral sediments, from all new water.
Click on any image
for complete product and ordering information.
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!
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 SPIN or Pinpoint system, rather than a less
accurate test kit or strip reader.
LaMotte Professional Testing Center Locator I
hope that I have been helpful.
Sincerely. Alan Schuster, 6/27/2012
► Nitrates -
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.
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, 5/31/2009
► Is It
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
Sincerely. Alan Schuster, 6/1/2005
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
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
Sincerely. Alan Schuster, 5/19/2008
► Low Nitrate
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
Alan, are the ion exchange resins an
option for me ? I measured my nitrates at about 60-70 ppm,
and the only parameter not perfect in the pool is free
chlorine. Water is clear and no algae, total chlorine is
1.9ppm, free is 0.1 PPM.
Steve K., Wisconsin, 5/22/2010
Ion exchange is the only removal solution, other than water
replacement. However, you can minimize the effects of the
nitrates, by removing the phosphates. Both are vital algae
nutrients and phosphate removal, using
POOL REFRESH, is easy. Without phosphates
algae growth will slow down, even with nitrates present.
Add enough chlorine to boost your free chlorine to over 10
PPM and the combined chlorine (difference between total and
free) should come down. I hope this information proves
Sincerely. Alan Schuster, 5/22/2010
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 test strip such as the
Insta-Test Strips or, even better a
ColorQ All-Digital water
Analyzer, which provides the right kind of information. I
hope that I have been helpful.
Sincerely. Alan Schuster, 6/7/2006
Are nitrates a factor in pool water?
Should I test my customer's water for it? Thanks for the
John T., 4/23/2005
Maybe! Just finding a low level of nitrates does not
necessarily indicate a problem. You can't keep emptying
pools because of its presence. However, when a pool is
experiencing great difficulty controlling algae, even when
all reasonable steps have been taken to control the algae,
it might be a good idea to test for nitrates. This is
especially true if there is a known source for the nitrate
contamination such as agriculturally contaminated water.
Levels above 25 PPM are considered potentially problematic
and can result in increased chlorine consumption. To lower
the nitrate level, water must be replaced. If replacement is
not a viable option, try eliminating the phosphates, using
POOL REFRESH, as this is the
next best option. I hope that I
have been helpful.
Sincerely. Alan Schuster, 4/23/2005
► Green Won't
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.
Sincerely. Alan Schuster, 8/11/2004
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
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 the
Insta-Test strips or a
all-digital water analyzer, which performs tests without
color-matching of any sort. as they provide the right kind of
information. Good luck and I hope that I have been helpful.
Sincerely. Alan Schuster, 5/24/2006
► Doesn't Add
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
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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