How to Lower Phosphates in a Pool

Reviewed by Andrada Simion, Master of Science in Chemistry

Not sure how to get phosphates out of your chlorinated pool? You have come to the right place:

  1. What are phosphates?
    Phosphates are just a chemical compound. They are made up of the chemical phosphorus, which occurs naturally and is not metallic. They are usually made up of a single phosphorus atom bound with oxygen.
  2. Why are phosphates bad for your pool?
    The primary reason that these chemicals are bad for your pool is that water based plants use them as food, and do not need very much of it to survive. The primary concern about phosphates is that they are going to allow algae to thrive in your swim area, resulting in murky and green water and a chemical imbalance.
  3. Do you really have to remove phosphates?
    In theory, they themselves are not an issue. However, the more of the chemicals there are in the water, the more likely you are to have algae growth in your water. Because of this, we recommend removing them as a preventative measure.
  4. How do phosphates get in your pool?
    They get into your outdoor swim area in a number of ways. For one thing, these chemicals are often carried into the water from the surrounding environment when leaves, twigs, and other plant life fall in. They can also be carried in by the swimmers or their clothing. In addition, chemicals used in or around the pool could bring phosphates in or, depending on the municipality, the water may already contain them by the time it gets to your pool.
  5. How do you prevent phosphates from getting in the water?
    Some of them are bound to get in your pool. That is not an inherently bad thing, it is actually very normal. You can prevent high levels by regularly skimming and monitoring the chemicals you use in and around the swim area. Cleaning the filters regularly and using an underwater vacuum will also help this from becoming a problem.
  6. How do you test for phosphates?
    You can buy a testing kit to do this, but because the compound takes a long time to build up it is not necessarily something to panic about right away. You may also just bring a water sample to your pool supply store and have them test it for you.
  7. Can you swim in a pool with high levels of phosphates?
    Yes you can. These compounds take a long time to build up and have to be present in extreme levels before they would begin to be harmful.
  8. How do you get phosphates out of your swim area?
    You can use a phosphate remover, typically a chemical containing a high amount of lithium, which will bind and remove the chemical. The water may have a filmy, white appearance immediately after use, but if you allow the water to filter it will dissipate. You can also try using calcium, which will also bind the chemical. In addition to these chemical treatments it is still highly recommended that you regularly do other pool maintenance, like skimming, cleaning filters, and vacuuming. If you have an overgrowth of algae an algaecide is also recommended.
  9. How soon after using a phosphate remover can you go swimming?
    Before swimming, you should allow the chemical treatment to circulate through the pool for about an hour. Once it’s been filtered through and the water is clear you are safe to swim.

So, there are lots of things you can do to lower the level of phosphates in your swim area. You can remove them chemically and keep levels low through routine pool maintenance. The chemicals themselves are not as much of a problem as the algae that feed on them, but keeping levels low is an important part of keeping your pool healthy.