What To Do if Your Swimming Pool Has Nitrates

Written by Michael Dean
August 24, 2023

swimming pool with nitrates

If you just did a chemical test on your pool and discovered that you have nitrates in the water, there’s no need to panic. While they’re not ideal, they’re relatively common and something many pool owners deal with at one point or another.

In this article, I’ll help you understand what nitrates are and how to get rid of them and prevent them.

Main Takeaways

  • Nitrates come from wells and septic tanks, lawn fertilizer, rain, animals and pets, manure runoff, and people.
  • To get rid of nitrates in your pool, identify the cause of the nitrates and remove them from your pool and then partially drain and refill the water.
  • If the nitrate levels are too high and your pool has turned green, you may need to completely drain and refill your pool.
  • To prevent nitrates from returning, regularly maintain your pool and test your water frequently.

What Are Nitrates?

Before you can learn how to treat your pool for nitrates, it helps to know what they are. Nitrates are chemicals and a plant nutrient naturally found in certain foods, the air, and water. And in this case, your swimming pool’s water.

Wherever there are plants, there are nitrates. So because they’re a plant nutrient, you’ll likely find some nitrates in your pool water if there are plants around your pool.

Where Do Nitrates Come From?

You can’t prevent high nitrate levels in your pool water if you don’t know where nitrates come from in the first place. Nitrates come from several sources, and where you live can also play a factor. Here are some of the top sources that have contaminated your pool water with nitrates.

Wells and Septic Tanks

One of the most common ways nitrates make their way into your swimming pool is via a well or a septic tank. Septic tanks naturally have nitrates in them that can get into the ground before turning up in your pool.

A well generally contains a lot of nitrates as well. If you use well water to fill your swimming pool, nitrates will likely appear on a chemical test. Hopefully, they won’t be at an unsafe level for swimming, but it’s best to do a chemical test regularly if you use well water.

Lawn Fertilizer

Using fertilizer on your lawn or other plants can contribute to nitrates in your pool. Even without the use of fertilizer, nitrates are plant nutrients that can contaminate your pool. Using fertilizer increases the risk of finding high levels of them in the water.


If you’ve ever seen or heard of people covering their pool before it rains, there’s a reason. Covering your pool can help prevent nitrates from the rainwater contaminating your pool. But, unfortunately, sometimes the rain comes without much warning.

Therefore, having your pool covered after use and until you use it again is the best way to prevent nitrates from the rain from getting into the water.

Animals and Pets

Pets and other animals are another common cause of nitrates in your pool. For example, if you have a dog that enjoys swimming in your pool with you, nitrates from their fur and paws can transfer into the pool.

Other animals besides your pets can have nitrates that get into your pool water. Anytime birds or ducks land in your pool, their feces can contaminate the water.

Manure Runoff

Manure can contaminate the water for those who live in rural areas or have horses or cattle. This typically happens when it rains, and the runoff from the waste enters the pool.


This may surprise you, but humans can also contribute to small traces of nitrates in pool water. Oils and sweat may only cause a small number of nitrates to be found in your pool, but in combination with other common causes of nitrates that we’ve mentioned, this could grow into a more significant issue.

When you go swimming in a pool, and you have on any cosmetics or toiletry items, they can also have trace amounts of nitrates that transfer from you to the water.

If you have a little one swimming in the pool, any accidental waste will also cause nitrates to appear on the chemical test.

How To Get Rid Of Nitrates in Your Swimming Pool

If you can discover the nitrates in your pool early, you may efficiently treat them. But, if the nitrates have been in your pool to the point when the water is turning green, you’re going to have a more difficult time removing them.

The first step to treating your pool water for nitrates is to decide if the current pool water is worth treating. If the water hasn’t turned green and the nitrate levels aren’t incredibly high, it’s possible to treat the water.

Identifying the cause of the nitrates in your pool and removing them may prevent your water from becoming highly contaminated.

The next option for treating your pool water is to drain the water partially. Sometimes only partially draining the water and then adding freshwater can remove enough nitrates so that the water is safe to swim in again.

When you’ve tried both options, and neither seems to work, that’s when you’re at the last resort. Typically the pool water has turned a shade of green at this point, or the nitrate levels are too high. You’ll have to drain the pool of water and refill it completely. You can read my complete guide on how to clear a green pool for instructions.

It may be a pain to do, but it will ensure that all the contaminated water is out of the pool.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

Something went wrong. Please check your entries and try again.

How To Prevent Nitrates From Coming Back

Once you’ve reached the point where the nitrate levels are incredibly low, or you’ve fully drained the pool water, you’ll want to do your best to keep them from coming back.

The best way to prevent nitrates from contaminating your pool at high levels is to perform regular swimming pool maintenance. How often you need to test your pool water is dependent on a few factors.

You’ll need to test your water more frequently if you use it often. Another time you’ll want to test your water, even if it’s not part of scheduled maintenance, is after a heavy rainfall if you didn’t cover your swimming pool. I have an entire article on what to do to your pool after it rains, with a bunch of tips you can use for your pool.

As I mentioned, keeping nitrates completely out of your pool will be hard. When you’re regularly performing pool maintenance, you’ll want to look for nitrates in a range from 10 to 25 parts per million (ppm).

If it’s possible, you’ll want to do your best to keep it under ten ppm, but that range is still considered safe.

Final Thoughts

Nitrates are unavoidable when owning a swimming pool. While small amounts of nitrates in your pool aren’t a cause for concern, preventing them in the first place is the best method to keep your nitrate count low without having to drain your pool completely.

While they can be a hassle, they’re not a cause for significant concern. If you regularly schedule maintenance for your pool and keep on top of the water quality, nitrates will be a minimal issue for you.

Questions? Shoot me a message.

Scroll to Top