Phosphates In Your Swimming Pool

It’s funny that we never hear customers complain about phosphates being in their pool until their pool is green. Did you know that phosphates are always in your swimming pool, even when there are no algal blooms? That’s because it doesn’t cross your mind when your pool is nice and blue. After reading through various articles and customers’ questions on removing phosphates, I’ve come to one conclusion, there’s a lot of misconstrued and misconceptions regarding phosphates in your swimming pool. What exactly are phosphates? Where do they come from and how do phosphates get into your swimming pool? What is the threshold for phosphates before it becomes harmful to the swimmer?

Let’s explore phosphates a little more.

What Are Phosphates?

Phosphates are nutrients that help increase plant growth. Naturally, you can find phosphorus material all around. That is why it is common for phosphates to be in your swimming pool. But how exactly do phosphates enter your pool? There have been many debates suggesting how phosphates enter your swimming pool. Some argue that excess rainwater or fertilizer can affect your phosphate levels. Which is true, sort of.


How Do Phosphates Enter Your Swimming Pool?

Phosphates might enter your pool one of several ways, but rainwater is not one of them. Rainwater itself isn’t phosphorous. In fact, it’s impossible as phosphates do not atomize in the atmosphere. However, once the rainwater runs off into the soil, then it becomes phosphorous. Usually, swimmers bring the majority of the phosphates into the pool with them. Contaminants like makeup, lotions, shampoos, dirt, leaves, and other pool chemicals like scale and stain products account for the majority of the phosphates in your pool.


When and How You Remove Phosphates From Your Pool

Whenever you have an imbalanced pool, one of the first things you should do is test your water. Before you can remedy the issue, you first need to determine what the issue is, right? So what happens when the store clerk tells you your water has a high amount of phosphates? Naturally, the first thing pool owners do is go out and purchase a phosphate remover and add it into their pool.

If you’ve already experienced this, you already know that this won’t solve your green pool. Now, you have a green pool AND white sediment at the bottom of your pool. The first thing pool owners should focus on is removing the algae. In this particular case, once the pH and alkalinity levels were correct, the water was clear. To be honest, there probably wasn’t a need to purchase the phosphate remover. In most cases, you won’t have a need for phosphate remover.

In fact, there is no scientific evidence that even proves that phosphates actually increase algal growth rates when phosphate levels are below 1000 parts per billion (ppb). McGrayel Water Technologies completed a study and it was determined that algal growth rates are unaffected at each phosphate level. They also determined that phosphates are not likely to be a problem until after levels are above 1000 ppb.

Before adding phosphate remover into your pool, make sure you actually need it. We do not recommend adding unnecessary chemicals into your pool. Remove phosphates from your pool when levels exceed 1000 ppb. Once your phosphate levels exceed 1000 ppb, I would consider purchasing a phosphate remover. Keep in mind though, phosphate remover will not rid your green pool.

Reduce the high cost of removing phosphates by being proactive. Keep in mind, phosphate remover is preventative, not a remedy. Test and treat phosphates annually. There isn’t a need to worry about them constantly. Instead, focus more on keeping your pool properly balances.



55 thoughts on “Phosphates In Your Swimming Pool

  1. Very helpful article! All my pool water samples in the summer were balanced except for slight problems with pH being too high, which we would treat with muriatic acid or pH Down. The phos always hovered right below the 500 which was noted as the “high normal “standard. I always worried about it but no more!! Knowing that 1000 is the limit helps a new pool owner! Looking forward to late spring 2018!!!!

    Thank you!

  2. Great information!! This site has given me a lot of knowledge about owning a pool. Many problems have been solved just reading the info posted in the email messages with the links to the articles. Keep up the great work!!!

  3. I’m fighting the phosphate battle right now. This is helpful. Had my water tested for phosphates. Came back really high. This is the first time EVER I’ve had this problem. The only thing I can attribute it to is that a high wind storm partially took off our [water bag] cover in the spring. Lots of yuck that was on top the cover mad its way into the pool water.

  4. I had my water tested and it was over a 1000.My water was a light green.I just added the remover today.I noticed some stuff on the bottom few hours later.Just wondering what i am to do after.All other levels are normal.I need the green gone

    1. Make sure you are cleaning the filter. You must use a phosphate remover and then clean the filter a day or so later. My levels went down only after rinsing off the cartridge filter.

  5. Great article. I appreciate what you do with this site. Very informative. My pool turned a cloudy green over the span of 3-4 days. I’ve cleaned my filter cartridges and took my water into our local pool store to have it tested. The chlorine and pH levels are in line and actually a little high. However the phosphates are at 1000. So try suggested adding calcium to lower the phosphate levels.

    Sounds like this won’t necessarily clear up the pool so I’m not sure what’s happening to the pool. The only recent event I can think of is we recently turned on a pump for a waterfall in the pool and noticed the water in the pool pump was very green. Could that have circulated algae into the pool which then started feasting on all the phosphates?

    1. It doesn’t matter how many phosphates are in a pool, if chlorine is present in a sufficient enough number algae cannot live. Take a look at our how to clean a green pool article and video. I’m not sure where the algae came from, but if there is cloudiness, then your chlorine is working. Cloudiness after an algae bloom is a sign the algae is dying. Add shock and algaecide, to expedite the process. Keep your chlorine levels elevated, until the green is gone. Add clarifier to clear the cloudiness after the green is gone.

      1. But it does matter how much phosphates are in the water, doesn’t it? The first year we had our pool we never had a problem, 2nd year it turned green once and the 3rd year (last year) it turned green like 6 times at least – every time we kill the algae dead algae makes mor phosphates which feeds new algae. I do agree with not putting unecessary chems in it though because it seemed like the more the pool store told us to put in our pool the worse it got… however I feel like if we had cleard the phosphates after an algae bloom was killed it might have helped us avoid the next which usually came within a week of the last.

        1. The long and short of it is, if you maintain proper chlorine levels, algae won’t grow. Phosphates are food for algae, but algae can’t eat if it’s dead. An easy way new pool owners get behind on chlorine production is not keeping your CYA in check, which inhibits the chlorine if the CYA levels are high. The water turns green even though you’re adding the same amount of chlorine tablets, but you are not accounting for the higher levels of stabilizer. This might explain your algae issue got progressively worse and worse.

  6. Hi
    I live in Phoenix with current temps around 110.I also have many trees around my pool that shed debris into my pool. My phosphates are reading at 500ppm. Also my Chlorine is reading high right now. I purchased POSfree per the recommendation of the pool supply store. When I was reading the label it states.

    Important- Do no test Phosphates if the Chlorine is high. My question is, should I go ahead with using the Phosphate remover?

    Thank you

  7. Hello
    I’m having a phosphate problem for the first time this year. My phosphates were tested to be approx. 4600 ppb. After treating with commercial grade Phosfree and the highest strength phosphate reducer it is still testing at 4000 to 5000 ppb. Is there anything left that I can try besides emptying the pool and refilling?
    Thanks in advance for you help

    1. I would go with another treatment of the phosphate remover. Maybe try a different band.

      When draining the pool, I wouldn’t drain the pool completely, just like a third or a half.

      1. It took me 5 treatments to go from 2000+ to zero, and takes attention to keep it below 500. Suspect organic crud through the screen from surrounding trees as the cause. No need to renew water. Once you get it to 500, weekly/2-weekly phosfree treatment should maintain it without cleaning the filter every time.

    2. Biodex phosphate remover plus, it’s expensive but the best chemical I’ve come across. Dropped ppb by 2000 overnight

  8. We have given up and drained the pool to start over. What will we do with many buckets of phosphates that we will have to scoop out of the bottom?

  9. I ve had my pool running since May 19th 24/7. First it was the usual alkalilne ,ph, shock. The it was metal remiver, followed by iron remover, tons of schock, and liquid shock , then finally phosphate remover, Not once but twice . My pool is cloudy cannot see the lunar net it hittom at all . Phosfate reading 4699. What can be done ?

  10. Is there a chemical compound substitute that I can use instead of the expensive PhosFree products..Example, I use soda ash to raise the PH,,can buy in bulk very cheap.

  11. My water is crystal clear. Phosphate at 2450 after one treatment of phosfree. Was at 2550. Only dropped 100 after first treatment. Chlorine is now gone. Our second treatment is in process. Should we see our pressure on a sand filter increase? We did not our first treatment and the pool supply store was shocked. We have a sand filter. This is our second year with it.

    1. After the treatment, did you backwash and rinse your filter? Also, some phosphate agents require that you bypass the filter media, by setting the multiport valve to recirculate. This is because those phosphate agents clog the filter. Did your instructions have this step?

      1. Yes we backwashed after the firat treatment The pressure never changed with the first treatmen. We back washed after the first treatment and have a sample tested again It only went down by 100.
        My questions are: 1- SHould my sand filter build pressure? 2 – is it noRmal to have the water be crystal clear with high levels of phosphates?

        1. As stated in my previous response, if you used a product that required you to bypass the filter media but you did not do so it could cause clumping and clogging.

          Yes, you can have clear water with high phosphates.

  12. The product did not require that I bypass the filter. it stated to pour in the skimmer and run for 48 hours and then backwash. we are on our second treatment. We don’t know what to do next

  13. We get results tomorrow. prIor to the first phosfree treatment we had used flock and clarifier As I mentioned pool water is crystal clear our biggest problem is being able to keep chlorine in the water That is why we had the water tested and they found it was high and phosphates They indicated that the phosphates eating the chlorine that is why we could not keep chlorine in the pool

  14. We are having exactly the same problem as Laurie. Took a water test today to pool place and said our phosphate was extremely high. We have shocked our pool 5 nights in a row and every morning there test say no free chlorine using test strips and by having water checked. Going to buy phosphate remover today. Looking for good product. Any help be appreciated.

  15. Phosphates down to 2400 after second treatment. Water still is crystal clear. I am getting conflicting opinions on whether it is necessary to treat these phosphates. My biggest concern is I can’t keep a chlorine reading in my water. One pool supply store is recommending we drain significant amount of water and at noon and the other is saying don’t worry about it just do what we would normally would do with chlorine and pH as long as the water still clear. It has been almost a week since we have been able to treat it with chlorine with the 85° weather at this point I need to worry about algae. Thougjts? where do I go from here?

  16. I just bought phosphate remover. We are gonna try the remover first. I went through all the forums and made a bunch of phone calls. Got alot of different answers but the most common answer was to treat the phosphate issue. Then introduce chlorine back into the pool. Please keep us informed.

  17. My phosphate level was 1000 and I was told to add PhosFight. My water was crystal clear before and all chems were balanced. After adding the phosfight, it’s cloudy. Instructions say to run filter for 24-48 hours then backwash. Is it normal for this stuff to make the pool cloudy?

  18. Same problem as others…2000 – got rid of algae – added remover – shocked it twice – can’t get a free chlorine reading – add clarifier – water is pretty blue but cloudy – starting to think draining the pool is cheaper…….

  19. Got mine down to a count of 100, down from almost 4000 count. Used phosphate remover took 5 bottles. Restocked the pool. Gonna wait two days then have retest done.

  20. They say my Phosphate level 1000, my pool is clear not green could this be a bad test or should i use phosphate remover. Also isn’t PH plus and Aklalinty Increaser baking soda, if i raise one of them will it take care of both problems.

    1. Just because your phosphates are at 1000 it does not mean your pool is going to start turning green. If your pool is clear, then I wouldn’t worry too much about it. As long as you keep the chlorine levels in range, you will be fine.

  21. Great article!
    We have a salt generator. This past spring I noticed that we could not hold chlorine in this pool for anything. I was shocking it every 2 days and the chlorine would be gone withim 24 hrs. I couldn’t understand what was going on. I thought the salt cell had gone bad in less than a year. Thankfully my husband does service and repair work for a pool company, and we were able to get a new cell without using our warranty. He does repair work and installation and does not have much experience with pool chemistry otherwise I probably would have figured this out sooner LOL! Anyways, new cell in place, and we blasted the pool with trichlor because we were treating for black algae too. Everything seemed to be pretty good for a few months.
    Last week the same thing started happening. The pool was loaded with algae. I couldn’t keep chlorine in it. I would shock it and run a boost and 24 hours later there be nothing in it. I wasn’t going to go through this again. There was no way we had two bad cells.
    I took the water down to have it tested. I told him what was going on. All of our chemicals were in perfect check. We had plenty of cyanuric acid. Our pH was 7.4. No chlorine though. They said this is probably a phosphate issue. They ran the tests and our phosphate levels were 1500. Way over the normal recommended limit. I bought the phosphate remover which was a little pricey. We spent the next 48 hours filtering out all the phosphates and residue. I think we washed the filter five or six times. That’s how much it was filtering out to the point it was so clogged that it would stop spilling over from the spa running at 2700 RPM. That is a severely clogged filter.
    4 days into this, the pool looks fantastic. The algae is gone the chlorine levels are holding between 5 and 7. I’ve got the salt generator running back at 35%. After this experience, it would be my guess that the other cell was never bad and this was the problem. I have read articles stating that high phosphate levels will compromise the performance of a salt generator. There was one site that would not acknowledge that. They said there was no scientific data to prove it. Well I don’t need scientific data because I just went through it and that’s exactly what was going on. Summing it up, based on our experience, if your phosphate levels are high it definitely affects the way your salt generator performs.
    Thank you for posting this article because you seem to be more willing to acknowledge that this is a real problem for people who owns salt generators.

  22. After using a phosphate starver my cell shut down as the cartridge was clogged with a white gluey substance. Is this normal that the phosphate converts to a white glue that you can just hose out of the cartridge?

    1. I have not heard of a white gluey substance in the filter stemming from the use of phosphate remover. It may be specific to the brand of chemical you used. If it is easily washed off the cartridge, then it shouldn’t be much of an issue. Did the instructions of your phosphate remover state to remove the cartridge or bypass the filter?

  23. i have been treating yellow algae for two weeks, using yellow out and the slam method on above ground pool algae still there. no trees around pool area. should I drain the pool and restart? its also equipped with salt water, Hayward equipment

  24. wish I had read this before my pool supply guy sold me a bunch of phosphate remover.My reading was only about 650. My water is crystal clear with a 7.2 pH and good chlorine levels. Am not going to add anything just yet.

  25. I had a clear pool until had water tested and was told needed to add no phos. We did that and now water is cloudy. How to get rid of the cloudiness??? Pump has been running for 48 hours and still cloudy.

  26. We have been struggling to keep chlorine in the pool. Every time I test it the strip is white. On days it is purple in the morning the color strip is white again after just an hour of the pool being opened. Our local pool store has been helping. We have added algaecide, and shock, and also phos free stuff. They said our phosphates are high. I never asked at what level they are.
    I have backwashed several times and superchlorinated several times.
    This last time we used a stronger phosphate remover and now there is white stuff on the bottom of the pool. It is not a gel. It is powdery. When I tried to vacuum it up it just swirls around. Do I need to worry about cleaning those out?

    1. Vacuum your pool bottom with the filter set to “waste” so that everything you pull off the bottom goes directly to the sewer and not back into your filter and your pool. It will work. Wastes some water, however.

  27. Hi Matthew. I’m a new pool owner, I’ve been caring for my 9800 gallon pool for just over 2 years. There’s so much to learn and I dread the consequences of any mistakes. I’m very thankful for someone like you to help.

    The pool store told me that my phosphates may be high since my chlorine is depleted. As far as I know, that’s the only reason he said that. Their free test doesn’t include phosphates, from what I can see. So they want me to do a treatment. Of course, I’d rather not do that if I don’t need it. My pool is crystal clear, a beautiful blue and the water is very soft and nice.

    I thoroughly brush the pool and skim and sweep 7 days a week. I clean my filter cartridge every 4 weeks and if we’ve had people in the pool (which isn’t often), I special clean it the next day. I usually keep a cover on the pool and it’s also screened in. There are no trees around it, so aside from some fine pollen and a few bugs, there’s little to no debris floating or sunk in my pool. For the most part, I’m the only swimmer and I use little to no grooming products. My daughter swims but also uses next to nothing in hair stuff etc.

    To get to the point, should I do a phosphate remover just because the pool store kid says I have no chlorine? There could be a few reasons that my chlorine is low, I’m thinking. The previous week, my water test said add nothing, so no chlorine was added for 2 weeks except a half gallon I added 5 days before the test. Also, since it’s summer (in FL), my pool is uncovered more the last 2 weeks. It spent the winter covered 90% of the time.

    Anyhow, sorry for the long post. But I wanted you to get an idea of my poll’s current state. I thank you for your help.

  28. My phosphates are around 5600 and that’s after a bottle of remover. The pool is a clear mint green color.

    1. From the article:

      Remove phosphates from your pool when levels exceed 1000 ppb. Once your phosphate levels exceed 1000 ppb, I would consider purchasing a phosphate remover. Keep in mind though, phosphate remover will not rid your green pool.

      Also, you have no chlorine in the pool, which is another major factor in why your pool is green. Algae can’t go in a properly chlorinated pool.

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