Understanding Phosphates in Your Pool Water and When to Use a Phosphate Remover

Written by Michael Dean
May 12, 2023

phosphates in swimming pool water

If you’re a homeowner who owns a swimming pool, you’ve probably heard that phosphates in your pool water are bad. But are phosphates really harmful for your pool? And do you need to purchase a phosphate remover?

Today, I’ll take a deep dive into phosphates, including what exactly they are, if they pose a problem for your swimming pool, and the pros and cons of using phosphate removers. Let’s get started!

Main Takeaways

  • You know your phosphate levels are too high if you have poor water quality, debris floating in the pool, and/or slimy surfaces.
  • Algae thrive on sunlight, water, and phosphates. However, if you have an algae problem, removing the phosphate won’t get rid of the algae. To do so, you need to use algaecide.
  • Using phosphate removers can reduce your phosphate levels to almost nothing and it may reduce your chlorine demand. However, they are not very environmentally-friendly, and they do not eliminate algae.
  • To prevent phosphate buildup, you should balance your pool water and clean your pool regularly. And when you do lawn work, be careful not to let the grass, fertilizer, and debris fall into your swimming pool.

What Are Phosphates?

Phosphates are chemical compounds that have phosphorus, an element that’s naturally occurring. Phosphates also have amounts of oxygen and hydrogen, in addition to other factors. Depending on your pool water levels, these inorganic materials can potentially cloud your water.

How Do Phosphates Get Into Swimming Pools?

If your swimming pool is outdoors, like most swimming pools are, you’ve got to remember that it’s exposed to the elements. That means your pool gets plenty of sunlight and deals with rain and other contaminants — like fertilizer or landscaping chemicals — introduced to your swimming pool through run-off. Even leaves in your pool can add phosphates.

It’s possible for pool owners to accidentally add phosphates to pool water if they’re using chemical products that have phosphorus materials or phosphoric acid.

How Do I Know If My Phosphate Levels Are Too High?

Ideally, you’ll want your phosphate levels in your swimming pool to be under 100 ppb (parts per billion). You can use a testing kit to find out exactly how much phosphate is in your pool, but you can also tell if your phosphate levels are too high by examining your pool visually.

Although these might not be signs of solely high phosphate levels, your swimming pool might have too much phosphate if you notice:

  • Poor water quality (green, cloudy water)
  • Debris floating in your pool
  • Slimy surfaces

So, that being said, are phosphates really a problem for your swimming pool?

Are Phosphates in Pool Water a Problem?

This is the $100 question, isn’t it? After all, you’ve probably heard pool chemical stores claiming you can control algae blooms only by eliminating these “harmful” phosphates from your swimming pool water. Algae needs only a few things to thrive: water, sunlight, air, and (you guessed it) a source of nutrients, like phosphates.

Well, it depends. Phosphates pose an issue in natural bodies of water — like lakes and streams — and drinking water sources, as these phosphates encourage algae growth. Luckily, your pool isn’t a source of drinking water, and it’s not a lake or stream either.

Although algae indeed gets nutrients from phosphates — and the more phosphates your pool water has, the quicker the algae will grow — removing these phosphates won’t get rid of an algae issue.

If you’re considering removing the phosphates in your pool to keep algae from growing, forget it. These phosphates aren’t harmful or toxic. If algae is your pool’s issue, use an algaecide regularly, and shock your pool at night for the best effects (I cover all the steps in my article on shocking a swimming pool). You’ll also need to keep those chlorine levels in check, too. However, a phosphate level of under 100 ppb is perfectly fine.

Because you’re a pool owner, chances are you’re already using a sanitizer like chlorine in your pool, which makes it an inhospitable environment for algae. If you also use an algaecide as recommended above, the chances of your swimming pool developing an algae bloom are lowered even more.

You can also do your best to keep your pool clean, which can do wonders for preventing phosphate buildup. When you brush your swimming pool on a regular basis, it prevents algae growth.

If you’re considering adding a phosphate remover to the mix, just know it’ll be another chemical you’ll have to spend money on. So are phosphate removers worth buying? Like most subjects, there are advantages and disadvantages to using a phosphate remover.

Pros and Cons of Using Phosphate Removers

Phosphate removers aren’t always the answer. Here are some pros and cons of using phosphate removal agents.

Benefits of Using Phosphate Removers

The most apparent benefit of phosphate removers is that many can lower your swimming pool’s phosphate levels to almost nothing. Although maintaining a proper sanitizer level with frequent brushing and vacuuming is the best way to prevent algae, a phosphate remover can also remove the phosphates to halt algae growth.

Another benefit is with regular phosphate removal; you may find your chlorine demand is reduced because the growth rate of contaminants has been reduced. Chlorine can stay ahead, and as a result, the water can stay cleaner.

It’s important to note that many phosphate removers are non-toxic; therefore, after using a phosphate remover, you’ll be able to use your swimming pool right after, unlike chlorine shock, where you have to wait some time.

Problems with Using Phosphate Removers

If you are looking for environmentally friendly ways to care for your swimming pool, phosphate removers might not be the answer. Lanthanum, one of the most popular active ingredients in phosphate removers, is moderately toxic to some living organisms.

To maintain a balanced ecosystem, oxygen must exist in the water source for organisms to survive. When algae die, it releases stored phosphates for more algae to feed off of. The effects phosphate removers have on the environment can be toxic.

Phosphate removers won’t eliminate algae and keep you from having a green pool. You’ll have to invest in an algaecide or improve your chlorine levels to do that. Keep this in mind if your pool water is looking green due to algae. There is no need to use a phosphate remover if you’re already using chlorine to maintain a healthy pool.

If you use a phosphate remover after a phosphate-based sequestrant, you’re canceling out the effects of the sequestrant because the most effective metal sequestrants are phosphate-based.

Phosphate removers can also cause cloudy water sometimes. You can read my entire article on phosphate removers and cloudy pool water to learn how to fix it. Too much phosphate remover in your pool can also be an issue.

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Effects of Phosphates on Saltwater Chlorinators

If the phosphate level in the water grows above a normal level, it can interfere with a saltwater chlorinator system. The algae will grow faster because the phosphates are food for it. The chlorine in your pool will work toward killing the algae instead of sanitizing the pool. This will cause the chlorine level to drop, thus leading to the idea that high phosphate levels lead to insufficient salt and create a negative downward spiral of bad pool health.

A coating of the phosphates on the electrodes can slow down electrolysis, disrupting the electrical current. This is the fundamental key to a function’s saltwater system. The salt cell and electrodes need to be clear of corrosion and metal sticking phosphates for the electrical current to flow.

Phosphates in a Saltwater Pool

Various situations can arise for phosphates to end up in your saltwater pool at unhealthy levels. Maintain proper pool hygiene, test your pool often, and do a chlorine shock if you feel your pool contains too many phosphates. It’s important to check that your chlorinator is built to handle the size of your pool and add more chlorine if needed. Ensure your considering all factors before using a phosphate remover.

Preventing Phosphate Buildup Without a Phosphate Remover

So, what do you do if you want to get rid of your swimming pool’s high levels of phosphates, but you don’t want to purchase a phosphate remover? What then?

One of the best methods for preventing excess phosphate growth is to take care of your pool as best you can. Balance your chemical levels on a regular basis (pH, chlorine, alkalinity levels, etc.). If you live in a constantly sunny area and you have high phosphate growth, you should be brushing your swimming pool regularly (at least weekly) to prevent algae buildup too.

If you ever see things like bugs, sticks, leaves, frogs, or other debris, get rid of them as soon as you notice them. To be more on top of eliminating waste as quickly as possible, empty your pool’s skimmer baskets regularly. This will help you get rid of that harmful junk quicker and encourage water circulation.

On the other hand, if you’re ever doing lawn work outside, be very mindful of your surroundings. You don’t want grass, fertilizer, or other debris ending up in your swimming pool, contributing to the high phosphate levels.

Although it’s entirely up to you as the pool owner if you want to use a phosphate remover or not, it’s essential to realize that there are other options — from algaecides to chlorine to other sanitizers — so don’t feel boxed in by the idea of a phosphate.

The bottom line? Phosphate removers aren’t necessary for the success of your swimming pool. No matter your choice, the most important thing is that you’re getting the most out of your swimming pool and not letting algae get in the way of your fun.

Questions? Let me know.

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