A Beginner’s Guide To Using Pool Stabilizer (Cyanuric Acid)


In today’s guide, you’re going to learn everything you ever wanted to know about pool stabilizer (aka cyanuric acid).

When you’re done reading this post, you will know:

  • What pool stabilizer actually is
  • Why your stabilizer needs to be balanced
  • How much stabilizer to add to your pool
  • How to correctly add stabilizer to your pool
  • How to raise and lower your stabilizer levels
  • The best stabilizer test kits to buy

Sound good?

Let’s dive in!

What is pool stabilizer?

Did you know that without a buffer, the sun can consume up to 90% of your pool’s free, unstabilized chlorine in just a couple of hours? 

Cyanuric acid, or CYA as it is commonly called (and also called pool stabilizer, pool conditioner, or chlorine stabilizer), acts as that buffer, protecting your chlorine from those hungry UV rays.

You can get it in liquid or granule form, or mixed with chlorine tablets or sticks (trichlor) and in chlorine shock (dichlor).

It’s usually just added once at the beginning of each swim season, but most chlorine products you buy also contain CYA, so your swimming pool should be getting a steady dose.

Why does stabilizer need to be balanced?

I don’t need to tell you the importance of chlorine. And because CYA shields your pool’s chlorine from being eaten up by ultraviolet rays, it’s an important chemical.

If your CYA levels dip too low, your chlorine will be completely gone in a few hours and your swimming pool will become susceptible to bacteria and algae growth.

If the pool stabilizer levels get too high, however, it overpowers the chlorine and makes it less effective. It can even lead to chlorine lock, making chlorine tests read negative even when you know there is some in there.

The only pools that don’t require CYA are indoor pools. 

Unless your pool is exposed to sunlight, it should be able to maintain the right chlorine levels fairly well.

How much stabilizer does your pool need?

Opinions vary a little among experts about the proper level of CYA a pool should have, but as a general rule, it should not dip below 30 ppm or rise above 50 ppm.

Some experts argue that it will be okay up to 80 ppm, but I disagree.

Most of the time, levels above 50 ppm cause chlorine lock, which is where you have added plenty of chlorine but your tests are reading 0.

You’ll still need to monitor your available chlorine levels with your chlorine stabilizer at 50 ppm or lower; you can do this with consistent water testing.

A good rule of thumb is to keep your sanitizer levels at round 7.5 percent of your stabilizer. So, doing the quick math, if your pool conditioner is 50 ppm, you should shoot for free chlorine levels between 3 ppm and 4 ppm.

You should use about 4 lbs of CYA per 10,000 gallons of water for every 30 ppm it needs to be raised. Some product instructions vary, though, so be sure to read the label for proper dosage. 

Most of the time, you will need to add CYA at the beginning of swim season and won’t have to mess with it much after that. 

P.S. this handy little calculator helps with dosage calculations for your pool chemicals. 

How to add stabilizer to your pool

Most manufacturers say to add your CYA to a bucket of warm water first and others say you can pour it directly into the pool.

I recommend always dissolving it in a bucket of water since it is an acid that can cause skin irritation or pool liner damage.

Just pour the product into your bucket and pour the mixture around the edges of your pool.

Never pour chemicals directly into your skimmer.

What if your stabilizer is too high?

I talked about chlorine lock earlier and this is what can happen if your CYA levels are too high.

This is why it’s really important to keep it balanced!

There is a chemical available called a CYA Reducer but there is still a lot of debate about whether or not it works. If it’s something you’d rather try before you dilute your pool, however, there it is!

Bio-Active BA-CAR-08 Non Polluting 100-Percent Cyanuric Acid Reducer Powder for Commercial and Residential Swimming Pools, 8 Ounces.
  • Reduces cyanuric acid levels by up to 50%
  • Eliminates chlorine-lock due to a high cyanuric acid level

The most reliable way to reduce CYA levels is dilution. That means you will need to drain a portion of your pool water and add fresh water to it. 

Unfortunately, this is not a chemical that will deplete on its own. 

What if your stabilizer is too low?

You usually won’t have to add CYA to your pool after the initial dose at the first of the season, but sometimes it’s necessary.

For example, if your pool water has been lowered for some reason (think huge pool parties with splashing kids) or if you’ve had some rainfall. After any of these events, it’s a good idea to retest your CYA levels. 

If you’ve determined that the levels are too low, go ahead and calculate the amount of CYA you need in order to bring it back above 30 ppm.

Dissolve it in your bucket and pour it around the edge of your pool. Retest again in about 24 hours. Repeat if necessary.

Pool stabilizer test kits

Most of your complete pool test kits or test strips that you buy will include a test for CYA, but if not, or if you would rather purchase it separately, here are a couple I recommend:

Blue Devil

Blue Devil Cyanuric Acid Test Kit for Swimming Pools, 4 oz.
  • VIAL INCLUDED: Testing vial is included in Cyanuric Acid testing kit
  • DETERMINE ACID AMOUNTS: Determine cyanuric acid levels in pool

This one contains enough chemical to do about 6-8 tests on your pool and it’s extremely accurate. 


Pentair R151226 79 Cyanuric Acid Test Kit
  • Cyanuric acid test kits
  • Determine parts per million of Cyanuric Acid

Another very reliable kit, this one contains enough solution to perform several more tests than the Blue Devil kit. It’s good for at least 10. 

Alternatively, you could take a water sample into your local pool store to have them test it for you.

Bottom line

If you have an outdoor pool, there’s not much getting around the need for a pool stabilizer to protect your pool from chlorine loss.

If you don’t use CYA, your pool’s chlorine will be almost completely gone in a couple of hours and your pool will be at risk for algae and bacteria that you just don’t want on your family.

On the flip side, like we talked about earlier, if your CYA levels are too high, it will diminish the effects of the chlorine almost completely.

On either side of the spectrum, you are leaving your pool water susceptible to unwanted junk and that means not only dirty water, but more work for you when it comes time to clean!

The bottom line is that using CYA is completely necessary even though it’s one more chemical you have to test and keep balanced if you don’t want to leave your pool open for attack. 

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