Nitrates in Pool Water

Lately, you notice that your pool has been consistently turning cloudy and green. You’re told that nitrates could be the probable culprit which made you blurt out “Why my swimming pool has nitrates and what should I do”?

The build-up of nitrates is a common pool problem which should be addressed immediately to avoid a more severe condition.

You may not be aware of the presence of nitrates in your pool as it is often overlooked not until its effects are visible.

The only solution to this problem is to drain part of your water or worse is to drain all of your water which would be very inconvenient. However, this could be prevented by keeping nitrates in control in your pool.

Understanding Nitrates

“Why my swimming pool has nitrates?” Nitrates are naturally occurring inorganic compounds that can be found in the soil, plants, in our bodies, and even in the food that we eat.

They won’t cause us harm unless they are taken in large quantities just as they won’t cause problems to your pool if you maintain it at an acceptable level.

Why are there nitrates in the pool?

Here’s an answer to the question“Why my swimming pool has nitrates?” Since nitrates can be found everywhere, its presence is inevitable in your pool. It is normal that your pool has nitrates, a 10-25 ppm level wouldn’t cause any alarm but above this range would make you consider doing some actions regarding the increasing level of nitrates.

If you let it loose, then you’ll face a tough consequence – its removal from your pool. Unlike phosphates, there are no available chemicals that could remove nitrates from your pool.

Where do these nitrates come from?

Nitrates that abound in nature could be easily introduced into your pool with the help of agents such as wind, rain, animals, and man. Below are the common sources of nitrate contamination in your pool.

  • Fertilizers

Inorganic fertilizers which are added to promote plant growth have nitrates as its primary component. It could directly or indirectly contaminate your pool.

If you are not careful, wind-blown fertilizers could go directly to your pool when applying it to your lawn or plants in your pool area.

Run-off water could also transport nitrates from the soil and plants into your pool.

  • Birds and other wildlife.


Birds and other animals such as ducks, if allowed near or in your pool can contaminate your pool with nitrates through their droppings.

Screened pools, especially can allow birds to perch and quickly deposit their nitrate-rich excrements.

  • Pets

Nitrates from your plants that could have attached to your dog’s hair could be easily washed off if they got to swim in your pool.

  • Human wastes.

Sweat plus cosmetic product residues such as make-up, lotion, shampoo, etc. from swimmers could contribute gradually a significant amount of nitrates in your pool.

Similarly, urine and feces particles can increase your pool nitrate level dramatically.

  • Rainwater.

Rain that is added to your pool could be a great contributor of nitrates in your pool.

  • Tap water.

This could be the least contributor of nitrates but if it is identified as the cause of your nitrate problem, then no draining and refilling will solve your problem.

  • Nitrates.

Another inorganic compound found in nature, in some conditions, air could combine with chlorinated water in your pool and become nitrates.

Nitrite (NO2) could also gain oxygen when mixed with your pool water to produce nitrate.

What are the effects of nitrates on your pool?

The presence of nitrates in your pool won’t cause any direct harm to you. It’s the quality of water that will be greatly affected since high levels of nitrates could make the following things possible.

  • Nitrates accelerate algae growth.

Nitrates being a food source for algae encourage their growth. The algae can attach itself to the walls of your pool though most of them will be found floating on your water.

In no time, untreated algae could cover your pool walls and floors.

  • Nitrates turn your pool green.

Nitrates don’t make your pool green, but it’s the uncontrolled algae growth that renders the green color of your pool.

It also reduces water clarity that’s why you have a green pool that is cloudy.

  • Nitrates make chlorine consumption shoot up!

The presence of high levels of nitrates in your pool will require you to add chlorine more than the usual amount you use in sanitizing your pool.

To be able to achieve the residual chlorine that safeguards your health, you tend to add more which means additional maintenance cost.

  • Nitrates cause poor water quality.

The presence of algae, a green cloudy, and unbalanced water are all indications of a poor water quality.

  • Nitrates make your pool unsafe and unhealthy.

Ultimately, the above- effects of nitrates boil down to one thing – unsafe and unhealthy pool.

What should you do?

You should identify and if possible eradicate the sources of your nitrates. Then, get rid of the nitrates in your pool either by dilution (draining a portion of your water) or elimination (draining all your water) and finally, refill it from a nitrate-free water source.

Keeping nitrates in control is the next thing to do!

The best way to prevent nitrate contamination in your pool is to ensure that your nitrate level is within the tolerable range of 10-25ppm.Or better yet maintaining it below 10 ppm where pool shock and algaecides are most effective in controlling algae at this level.

Regular water testing and maintaining chemical balance are most reliable to counter the effects of nitrates in your pool.

Check for phosphates too!

Just like nitrates phosphates are a food source for algae and have the same effects in your pool. Use phosphate removers (check this) which are effective in reducing phosphates in your pool without making your water cloudy.

Lesson learned.

Watch out for nitrates in your pool!  Don’t wait until its effects are apparent. Always check the nitrate level and keep it in control.

Putting nitrates in check should be part of your regular pool maintenance routine. Prevention indeed is the best way to avoid nitrate problems in your pool.

Hopefully, this article about “why my swimming pool has nitrates” was able to help you.

Worry-free swimming, anyone? Keep nitrates at bay!