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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.

author avatar
Charlie Ramirez
Writer at InyoPools.com, brings a wealth of knowledge and expertise in pool care and equipment, helping pool owners make informed decisions for over a decade.

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107 responses to “Phosphates In Your Swimming Pool”

  1. Linda Cronk Avatar

    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 ?

    1. Matthew Simmons Avatar

      Stain removers and metal sequestrants can cause a spike in phosphates. Since you added so much metal remover, you probably have to re-dose phosphate remover.

  2. Laura Avatar

    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?

    1. Matthew Simmons Avatar

      A garbage bag would be a good solution. Pour down storm drain if they will let you do so in your area.

  3. Jim Avatar

    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. Matthew Simmons Avatar

      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. Jeffrey Avatar

        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. Jeremy Avatar

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

  4. ldavis Avatar

    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

    1. Matthew Simmons Avatar

      Does it say not to test for or not to use the phosphate remover while the chlorine is high?

      1. Faith Avatar

        Yes it says do not treat with phosfree if the chlorine is above 5. This year upon opening our pool no debris was in it but it was an unslightly dark green. We shocked, did algaecide last Tuesday and it was left cloudy with no chlorine registering we shocked again after everything else was balanced and the chlorine went sky high. Been cleaning out filter cartridge (two new ones swapping out) and still cloudy you can maybe see a foot down into the water but it’s blue. Tested the water today and phos was at 3600! I used the whole bottle of phos free as suggested and you are to wait 48 hours with pump running and then rinse your filter. My alk which was slightly low when tested at the pool place is now sky high and the pH fell down. I’m not even going to attempt to mess with anything or retest until 48 hours now. I’ve never had this much trouble. Lesson learned buy a better pool cover this fall…..

  5. Jeff Jones Avatar

    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. Matthew Simmons Avatar

      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.  Avatar

        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. Matthew Simmons Avatar

          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. Mary Avatar

    My phosphates are like 3700….and can’t get them down!! And have been fighting mustard algea…

    1. Billy Sentry Avatar

      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.

    2. JAY HODSHON Avatar

      MINE ARE 3800 I USED 100 + OZ. LESLIE’S NO PHOS 2 TREATMENTS THEY WERE 4800 WHEN I STARTED! WATER IS CLEAR AT $ 58.00 A BOTTLE I’D LIKE A CHEAPER WAY TO GET THEM DOWN….

      1. Matthew Simmons Avatar

        Draining a portion of your pool water will remove phosphates. That is a pretty cheap solution.

    3.  Avatar

      Me too☹️

  7.  Avatar

    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. Matthew Simmons Avatar

      The green is algae, and you need to concentrate on getting rid of that first. That will involve a bunch of shock, algaecide, and backwashing. Take a look at this: How to Clean a Green Pool?

  8. Mike Avatar

    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.

    1. Do Avatar

      Took my water into Leslie’s Pool They said phosphates are high , They said to drain half the water out and put fresh water in there is no algae in my pool that I could see but it’s a little milky what should I do and can the kids swim in it it seems like the chemicals are pretty close to being balanced

      1. Bruce W Paso Robles CA Avatar

        Be careful of Leslie’s Pool. They said my phosphates were high (200 ppb – not high at all!) and sold me a $60 bottle of their “Perfect Weekly” which doesn’t even say what the ingredients are, or how much to add. It seems to be some kind of enzymatic additive with maybe a surfactant to slow evaporation, but I have a pool cover for that. I plan to return this stuff and look elsewhere for pool supplies. I have enough people trying to sell me “snake oil” as it is. I’m all for supporting “brick and mortar retail” that provides a service but I don’t care to be ripped off by them either.

        1. Matthew Simmons Avatar

          Thank you for your story, Bruce. In my earlier days, I’ve been upsold on the fancy new chemical of the month. I’ve learned that if a salesman brings up a brand new product that is “guaranteed” to fix my issue, I do my research before pulling the trigger. Chances are, it usually is some kind of basic enzyme cleaner that is just a general clarifier or sequestrant.

      2. Matthew Simmons Avatar

        As long as the chlorine levels are not over 5ppm, you should be good to swim. Is the water milky due to the chemical treatment or do you believe it is because of the phosphates?

  9. Tom Defino Avatar

    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!!!

      1. Jan Avatar

        Hi my phosphate are very high I have treated it with the phos free when I back washed it the first time looked like rusty dark brown water. Treated as directed with back washing and all. Now the water is beautiful but it’s still testing off the chart for phosphate. What now? Never ever had a problem with This before

        1. Matthew Simmons Avatar

          If the water is beautiful then it doesn’t seem like you have anything to worry about. As I have said countless times in this comment thread, if the chlorine level is kept in the proper range algae cannot grow.

          Phosphates are food for algae, not the cause of it. Chlorine kills/prevents algae before it can gobble up any tasty phosphates.

          1. Janel T. Avatar

            Thank you so much for this info. We are ne owners to a 30k gunite saltwater pool. The local pool store keeps telling us to lower phosphatase due to them being over 4000! The pool is beautiful and all other thing are in perfect balance. We have spent hundreds of dollars on their products that aren’t bringing the phosphates down. Every time we treat the pool looks Murky and grey settlement all over. If we can ever get it clear I think I will just do some algae guard and call it good.

  10. Betsy Y Avatar

    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!

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