How to Lower Phosphates in Your Swimming Pool the Easy Way

Michael Keenan


Pool Water Chemistry

High phosphate levels in your swimming pool is a terrible problem to have; not only does this increase algae buildup but also makes your pool water turn green. Today I will cover how to lower phosphates in a swimming pool.

Phosphates also cause a lot of other issues, as we will discuss later in this article. So, removing phosphates from a pool is inevitable.

With so much information available all over the internet regarding phosphates in swimming pools, it is important to be rightly informed about the issues at hand. Let’s look at what phosphates are, how they enter the pool and how to get rid of them.

how to lower phosphates in swimming pool

What Are Phosphates?

Phosphates are phosphorous chemical compounds that enable the growth of algae and aquatic plants. Apart from phosphorus, they also contain oxygen, and sometimes hydrogen.

They are derived from phosphoric acid which is found in all living and organic matter, including plants and humans.

Where Do They Come From?

Phosphates in your pool could have come from various sources, some of which can be the following:

  • High phosphates in your water supply
  • Runoff from garden fertilizer
  • Pool chemicals
  • Residue from skin and hair products
  • Human sweat
  • Detergents from bathing suits
  • Organic matter around the pool like twigs or dried leaves

Why Should Phosphate Levels Be Balanced?

Phosphates do not affect your pool water directly but lead to other problems listed as follows:

  • While lower phosphate values are not a problem, extremely high phosphate amounts, i.e., over 1,000 ppb, can affect your health.
  • High levels of phosphate also promote the growth of algae by feeding them. Algae growth is at a faster rate when high phosphate levels are combined with warm water and lots of sunlight.
  • High phosphate level, combined with algae growth, also uses the chlorine faster, thus making pool cleaning and maintenance difficult.

How to Test Phosphate Levels

You can notice high phosphate levels if your pool water tends to get green or cloudy because of algae growth. Most of the generic pool water testing kits do not include a test for phosphates.

A separate phosphate test is available that you can buy. You can also take a sample of pool water to your local pool supply store and get it tested by the store technicians.

Read this guide about unstabilized chlorine – who knew?

How to Reduce Phosphate Level in Your Pool

Here are a few methods you can try to reduce the phosphate level in your pool to acceptable limits:

  • Phosphates have to be removed by using specific chemicals that are designed for this very issue. Phosphate removers use lanthanum which binds with the phosphates and removes them immediately when added into the pool. This changes into a milky white color but that clears up within an hour.
  • Phosphate removers can be toxic as lanthanum is a metal which then remains in your pool water. Hence, these should be used sparingly.
  • Another way to reduce phosphate levels is to add calcium. This too binds with the phosphate and can then be filtered out. This method is also a great way to increase the calcium levels in your pool.
  • Algae removal methods like algaecides or shocking also help to remove phosphates. It is necessary to maintain phosphate levels below 100 ppb. Frequent shocking also helps to keep your pool clean while preventing algae growth.

What Happens If You Don’t Reduce Phosphate Levels

If you notice higher phosphate levels, it is necessary to deal with the issue as quickly as possible. High phosphate levels can lead to a lot of other issues such as these:

  • Phosphate acts as food for algae and other aquatic plants. With high phosphate levels, these can grow more and eventually cover your pool.
  • Phosphates also reduce the efficiency of chlorine in cleaning the water. With more organisms growing in the water, the chlorine added has a tougher task at hand and might not be able to keep up with the growth.
  • As chlorine usage increases, you will have to regularly check and maintain the chlorine level in your pool. This makes pool maintenance a very demanding task and also expensive.
  • Phosphates also combine with calcium to form calcium phosphates scales. These settle on the surfaces of the pool as well as any pool accessories like steps or stairs and damage those surfaces.

How to Reduce the Chance of Phosphate Buildup

When organic material, like dirt, dried leaves and other yard waste break down, they release phosphates. If such materials are close to the pool, it increases the rate of phosphates entering the pool.

So keeping organic waste away can help immensely. Here are a few ways to keep organic matter away from your pool:

  • Algae and phosphates feed off of each other to grow. So keep algae away from your pool and remove them as soon as you notice any buildup.
  • Algae get filtered so you might not notice the early onset of algae buildup. Check your pool filter regularly and clean or replace it. This might not remove phosphates entirely but you can at least ensure that any phosphates in the filter are removed.
  • Regularly skim your pool water to remove leaves, dirt and other organic matter. Before using, add phosphate remover to the skimmer so that you don’t add any external organic material to the pool.
  • A lot of times, organic matter also tends to sink to the bottom of the pool. This can get missed, so check and scrub your pool floor regularly. Using a pool vacuum is also a great way to do this efficiently.
  • Also, keep a check on the chlorine levels. By maintaining proper chlorine levels, you can keep the pool clean and prevent any kind of organic growth.

Final Thoughts

Maintaining the right chemical balance in your pool water is a great way to keep your pool water safe. There are multiple ways to reduce phosphates from your swimming pool, but with the right care and maintenance, you can ensure that this problem doesn’t arise.

With all of this information, keep an eye on your pool for algae growth, scaling or other issues and deal with them as soon as possible. Happy swimming!

michael keenan author

Author - Michael Keenan

I'm Michael Keenan the owner and creator of the Outdoor Care Guide. I'm a trained horticulturist with over 30 years of experience in pool care, plant care, and landscape care! Seemed like a good idea to share - I think I can make your life easier and save you some time and money!