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How to Reduce Cyanuric Acid (CYA) in a Pool in 2023

28. 5. 2020 last updated
  • Have you ever had a mysterious algae outbreak in your swimming pool despite having adequate chlorine levels and balanced pH?
  • Do you have a salt-water pool and your cell is seemingly not generating chlorine even though everything is functioning properly?

These are two instances in which a Cyanuric Acid, or CYA, becomes a vital ingredient for a properly maintained swimming pool. However it is very easy to reach levels of CYA that act counter productively.

There unfortunately is not many options for chemically reducing CYA levels in your pool. So depending on the size and location of your pool, the most common and practical way is dilution. Having said that, we’ll go over both of those options in this article.

Our tip

How to lower cyanuric acid (CYA) in a swimming pool?
The only sure method is dilution. However, it can be labor intensive or limited by environmental factors. There is a chemical route, but it may not work for some.

What CYA is and how it helps chlorine do its job

First things first, let’s talk about what cyanuric acid actually is. Often described as “sun-block” for chlorine, cyanuric acid (CYA) is most commonly found in 3-inch chlorine tablets used in maintaining swimming pools. It can also be added to pools separately in non-tablet form, most commonly to protect the free chlorine generated by a salt-water pool. When sold alone, it’s most commonly referred to as ‘chlorine stabilizer’ or ‘conditioner’.

Ultraviolet rays can quickly eat up any chlorine. So CYA acts as a chemical barrier to give the chlorine in your pool extra life.

Watch the video below by The Trouble Free Pool to learn more about the relationship of CYA and chlorine:

Great, throw in as much as possible then right? Sorry, I wish it was that easy.  Unfortunately, just like all the other chemicals in the pool, it must have a balance. Too much of a good thing can be bad. When CYA levels get too high they can actually chemically “lock” the free chlorine in your pool. Dilution is really the most economical and practical way for most of us to rein our CYA levels back to normal and get that chlorine back to work.

How to test your pool water for CYA levels

Levels should be at 30-60 ppm in salt-water pools and 70-80 ppm in non salt-water pools. You can test these levels with most pool test strips, the Taylor test kit  or by taking a water sample to your local swimming pool store.

You can see what the different levels of cyanuric acid (stabilizer) mean in terms of the amount of chlorine you need here:

CYA (stabilizer) Minimum free chlorine Recommended free chlorine Free chlorine for shocking
Pools without a salt water chlorine generator
20* 2 3-5 10
30 2 4-6 12
40 3 5-7 16
50 4 6-8 20
60 5 7-9 24
70* 5 8-10 28
80* 6 9-11 31
90* 7 10-12 35
100* 8 11-13 39
Pools with a salt water chlorine generator
60* 3 4 24
70 3 5 28
80 4 6 31
* Not recommended (source: thetroublefreepool.com)

Lowering CYA, Method 1: Dilution

Dilution is easier said than done. Basically, you just have to replace a whole lot of water (with high CYA) with a whole lot of other water (without CYA). Now, if you’re in south Florida, you can naturally have your pool water diluted and replenished by the afternoon summer rains. As long as you keep your eye on CYA levels throughout the rest of the year, you can depend on this natural dilution to keep your pool in check through the hottest parts of the summer, when you need chlorine the most.

However, whether it’s rainy where you live or not, there comes a time when you have to lower the CYA level and can’t wait around for a thunderstorm.

Before you get started

For this method it helps to have a basic knowledge of your personal pool and its equipment, i.e. pump/motor, and the general plumbing. In some cases a submersible pump will be necessary. 


You have to ask yourself several important questions.

  • How do I get a lot of water out of my pool?
  • Where will it go?
  • How/where will I refill the pool?

For some of us, the answers are easy. For others, these questions can be more difficult. First, you must have a basic knowledge of your pools plumbing. Every pool is slightly different.

How do you drain your pool? If you have a sand or DE filter, you can easily turn the handle on top to waste or backwash. If not, most cartridge filters have a drain plug on the bottom of the filter housing that you can easily attach a hose to. It takes a while to drain a lot of water through a small hose though.

I personally have to drain pools frequently in the summertime. I’ve found the easiest way to quickly drain a pool is to simply just take the top off of the filter housing. You must be careful of the flow of this much water in and around your pump area though.

How much water should be drained? Well, it depends on your CYA level. In many instances it can be up to 1/4 to 1/3 of your pool. An average pool is about 10 thousand gallons. 3 thousand gallons is a lot of water so you have to look around and think about how it will affect your environment. Will it kill your lawn? Will you be creating a hazard area (electric shock, slippage)? In some cases, you will need a submersible pump rather than changing any plumbing, and in some cases, there just isn’t a place to put all this water.


Okay, now it’s drained. Where do I get the new water? I wish it was as easy as just putting a hose in the pool for everyone. Thankfully, many pools I service are in areas where the main water source is free as they have their own well water. But for many of us water isn’t free and again… 3 thousand gallons going back in the pool is far from cheap. Sometimes, your local water supplier may give you a one-time break for filling a pool, but that varies by location. Doesn’t hurt to ask, right?


So now you have new fresh water in your pool and you can remember it’s a lot easier to monitor and maintain CYA levels accordingly. 3″ chlorine tablets are a staple to the pools I service but an unhealthy tablet diet is the leading cause of CYA getting unmanageable.

Lowering CYA, Method 2: Chemical way

Maybe your neighborhood regulations don’t allow the displacement of that much water or there just isn’t a viable spot anywhere in sight. The last thing we want is a whole neighborhood flooded with your pool water. If the dilution process works, awesome, but for those who couldn’t confidently answer those questions will have to go the chemical route.

There aren’t a whole lot of options to chemically reduce CYA in your pool. Bio-Active sells a CYA reducing chemical product. The back of the package offers proof of its effectiveness. In a video below, a tech tries a similar experiment in six of his pools he services. The results indicated the CYA was lowered in his pools, just not quite as significantly as the packaging said.

Natural Chemistry also has a 2 to 3 part chemical process for reducing CYA levels. Now, keep in mind it will most likely take more than one 8 ounce package of Bio-Actives product. This can be considered in the economical aspect of lowering your CYA. These products have simplified instructions on the packaging.

So your final question will most likely be, is it cheaper to buy several packages of chemical or is it cheaper to drain and refill?


Most importantly, you have to decide whether you have the time and space to drain and refill a significant amount of water to and from your pool. If you go the chemical route, that’s fine, but remember you and your loved ones might be in that pool. How much chemical do you want your body to be exposed to? These products are reportedly safe but if you’re like me, the less chemical the better.

So hopefully you will remember CYA the next time you test your pool, and the next time you get that mysterious algae bloom, you’ll have one more factor to cross off the list.

I hope this article came in time as you open and begin using your pools this summer. Please post a comment or share some of the experiences you’ve had with your pool.

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Article author

Peter Lloyd
Peter Lloyd

Author and editor with LeisureRate.com since 2017.

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