Phosphates In Your Swimming Pool: What You Need To Know


In today’s post you’re going to FINALLY learn what you should do about phosphates in your swimming pool.

Should you get rid of them? Ignore them?

How do you test for phosphates? Should you use a phosphate remover?

Everything you wanted to know about phosphates, we got you covered.

Let’s dive in!

Should you get rid of phosphates?

The short answer is maybe.

See, the thing with phosphates is that they are a food source for algae and aquatic plants. And even though there are other factors besides phosphate levels that cause algae blooms, this is one of them. 

But some studies show that they really only affect pool algae growth at extremely high levels of 1,000 ppb (parts per billion) or more.

So, monitor the levels but don’t get overly concerned when phosphate is present because it always will be.

What causes phosphates in your pool?

You have all kinds of uninvited guests in your pool every season—leaves, sweat, algae, you name it. And phosphates are no different. 

They are found in fertilizers, rotting leaves, skin and hair products, other pool chemicals, and even your water supply, as many municipalities add small amounts of phosphates to keep lead and copper levels low in drinking water.

This means that you can’t 100% remove phosphates from your pool, but the goal is to maintain them at levels below 1,000 ppb. 

How to test for phosphates

Now you know what your phosphate levels need to be, so how do you test them?

Most pool test kits and test strips do not come with phosphate tests, but you can get a phosphate test kit for pretty cheap.

However, because it takes such a long time for phosphates to build up in your pool, I always recommend taking a water sample to your local pool supply store to have it tested.

Their tests are usually much more accurate and you don’t need to do it more than once a year.

How to lower phosphates in your pool

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If your pool’s phosphate levels are actually nearing 1,000 ppb, you might want to consider doing something to lower them a bit.

One of the methods pool owners sometimes use is adding a product called a phosphate reducer, such as PHOSfree, which continually cleans the filter media and uses a rare earth metal to bind and remove phosphates upon use.

And if you have tried everything else and feel that needs to be done, you certainly can.

But it is my opinion that you should NEVER have to use this product!

For the most part, you can control phosphate levels by keeping the pool clean from debris and other organic matter. It also helps to keep your pool filter cleaned and the surface brushed.

After all, the main effect you want to prevent that phosphates lend to is algae growth. So, if you are keeping the algae population under control, you probably don’t have a phosphate problem.

3 common myths about phosphates

There is a lot of speculation and debate about phosphates and their effect on swimming pools, so let me just kill the most common ones right here.

1. Any amount of phosphates promote algae growth

While there is a lot of debate about this, most studies show that phosphate levels need to reach at least 1,000 ppb before they have any significant impact on algae growth to kill algae.

2. Natural elements are significant contributors to phosphate levels in the pool

Most pool experts claim that most of the phosphates entering the pool do so by rainwater, soil or debris.

While these elements do contain some phosphates, the most significant contributor is probably some of the pool chemicals you use, such as scale and stain-removing products.

3. Phosphates deplete chlorine levels in your pool

This is totally untrue and the two are completely unrelated.

Phosphates maintain their perfect oxidation levels all by themselves, so they don’t react with chlorine at all.

The great phosphate debate

So, if most negative information about phosphates is only partly true, then why the fuss?

First, a little history. Phosphorous was first discovered by Hennig Brand in 1669 while he was distilling urine for a study. He came up with an element that glowed and it has since been added to many household products and plant fertilizers.

Because phosphorus is an essential element for plant growth, it is used in fertilizers and other farm chemicals. It’s also an extremely effective cleaning agent when added to laundry detergents and other cleaners.

It’s also highly toxic in its basic state, able to cause skin irritation and even burns.

So, why use it?

Just like any element, in its most natural state, it can be harmful, but mixed with other ingredients, it usually poses little risk.

Take iron, for example. Iron is an essential mineral for the human body as a “key component hemoglobin that allows red blood cells to transport oxygen throughout the body.”

But if you get too much of it, you can suffer from iron poisoning and cell damage.

Should you use a phosphate remover?

As you’ve probably already deduced from the rest of this article, I don’t think anyone ever needs to use a phosphate removal agent. But let me tell you a little bit more about why I think it’s unnecessary.

First of all, phosphates in your swimming pool water are there to stay. You may as well accept it.

Secondly, if you are already making your pool water uninhabitable to algae, then there is really not much concern about phosphates.

Thirdly, phosphate removers can be more toxic to you than the actual phosphate. Some of them contain an element called lanthanum, which has been found to be toxic to humans and cause cancer.

And finally, it takes years for phosphates to reach unhealthy levels, and even then, an extremely high 1,000 ppb level is highly unlikely.

In short, why add more chemicals to your pool that probably are not going to make a difference anyway?

Six tips for keeping phosphates at normal levels

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Since I don’t necessarily advocate using phosphate reducers, what I do recommend is keeping them at manageable levels by doing a few key things:

  • Keep your pool free from debris by skimming out leaves and other plant life.
  • Brush your pool weekly to remove spores and buildup on the pool surface.
  • Use a good algaecide regularly.
  • Clean out the skimmer weekly.
  • Keep your pool covered when not in use.
  • Keep your chlorine, pH and alkalinity levels within normal ranges.

Bottom line

The truth about phosphates is it really is entirely up to you as to whether to take action against high phosphate levels or not.

Most experts agree that a little phosphate never hurt anyone. It is, after all, a natural element that in small doses is essential to life.

Your only concern should be if it rises to unsafe and unsanitary levels!

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