What Is Cyanuric Acid? Why It’s Important, Ideal Levels, How to Add It To Your Pool, and Much More

Written by Michael Dean
June 12, 2024

pouring cyanuric acid into a swimming pool

It can be a whirlwind to keep track of all the different chemicals needed to maintain a safe and sparkling swimming pool. Cyanuric acid (also called CYA) is a chemical most swimming pool owners will encounter, and it is important to learn how to use it.

In this article, I’ll walk you through all you need to know about what cyanuric acid is, its role in your pool, how to adjust your CYA levels, and more. Let’s dive in.

Main Takeaways

  • Cyanuric acid is a chemical stabilizer for swimming pools, which acts like a sunscreen for chlorine to keep it from prematurely breaking down under the sun.
  • Unfortunately, CYA lowers the overall effectiveness of your chlorine.
  • High CYA levels are often caused by using stabilized chlorine, such as dichlor or trichlor.
  • Always make sure to wear proper safety gear when handling cyanuric acid.

What Is Cyanuric Acid?

Cyanuric acid (also known as chlorine stabilizer) is a chemical stabilizer for swimming pools. Its structure allows each molecule to attach to three chlorine molecules. Although it is a relatively weak attachment, it does help stabilize your chlorine levels. This molecular structure is known as triazine.

Triazine includes three nitrogen (N) atoms, which will pair with chlorine. While it is paired, the chlorine is not as effective. But the use of CYA in your pool is still very important.

Although it is essentially a non-toxic chemical at less than 100 ppm, it can cause problems when too much or too little is in your pool. That is because cyanuric acid is a conditioner. Let’s cover why you use it in your swimming pool.

How Cyanuric Acid Works In Your Pool

CYA is necessary for outdoor pools, but not for indoor pools. You should also use CYA for saltwater pools. When the sun’s UV rays hit your pool, they can rapidly break down the chlorine in the water in just a few hours. CYA acts like sunscreen for your pool. UV rays will not damage chlorine molecules when they take shelter in the molecule of CYA. Cyanuric acid stabilizes the amount of chlorine in your water, stopping it from leaching out.

Chlorine is the most important chemical when it comes to sanitizing the pool. So having it essentially burnt out of the water on sunny days is not good for your pool. In fact, without cyanuric acid, you’d have to use up to eight times the chlorine to keep your levels right.

Think of the CYA as a floating umbrella. The chlorine grabs hold of it and floats along with the protective cover. While chlorine is bonded with CYA, it will not sanitize the pool, but since it holds a weak bond, it can break apart and clean when it needs to.

To better understand how CYA works, you should know about the different types of chlorine:

  • Combined chlorine: the chlorine that is used up and has already killed bacteria or algae
  • Free chlorine: unused chlorine that is freshly added to the water and actively sanitizing your pool
  • Total chlorine: sum of combined chlorine and free chlorine

Cyanuric acid is a stabilizer that bonds with the free chlorine in your water until it has killed bacteria or algae. Cyanuric acid conditions your water and keeps the chlorine at optimal levels, which means clear and safe water. However, too much CYA can cause even worse problems for your pool, so it is really important to test your levels and be aware of the cyanuric acid content.

Downsides of Cyanuric Acid

CYA lowers the effectiveness of your chlorine, slowing down its ability to keep your pool sanitary. The effectiveness of chlorine is called the ORP (oxidation-reduction potential), a measurement of how well the chlorine in your pool is working.

CYA should be used at the lowest effective level because regardless of how much you use, it will reduce your ORP. If you add too much CYA or allow it to build up over time, you’ll find your chlorine completely ineffective.

Chlorine will kill dangerous contaminants in your pool, keeping you and your family safe. However, it will no longer be effective if the sun dissipates your chlorine. Therefore, striking the right balance with your CYA level is pretty important.

Ideal Cyanuric Acid Levels and How to Adjust Them

According to the World Health Organization (WHO), the safe upper limit for cyanuric acid in your pool is 100 ppm. Still, you will not need that much to condition your water and protect your chlorine. Keeping your chlorine active is super important, so I recommend shooting for around 40-50 ppm.

What Causes High Cyanuric Acid Levels?

Your cyanuric acid levels may breach the recommended threshold for a few reasons. The most common cause of high CYA levels is the use of stabilized chlorine like dichlor and trichlor. These chemicals contain cyanuric acid, so using them will constantly add more CYA to the water. And because cyanuric acid will not go away on its own, the levels will consistently go up until you drain the water. Another scenario is water evaporating from the pool. When water evaporates, it will leave behind the CYA in a pool of less water, meaning the levels will be at a higher percentage.

How to Raise CYA Levels

Raising your CYA level is an easy process with only a few steps. Here is the necessary equipment to have on hand:

  • Acid-resistant gloves
  • Eye protection
  • Bucket for mixing
  • Pool water test kit
  • Cyanuric acid

Cyanuric acid is also called pool conditioner or pool stabilizer. It’s all the same thing. Here’s the brand I recommend.

Pool Mate Swimming Pool Stabilizer and Conditioner

Stabilizer is just a fancy name for cyanuric acid. Pool Mate makes a good product that is affordable.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Step one: Test the water

The first step in raising your CYA levels is to simply test the water (use a pool water test kit). Testing the water will allow you to determine the quantity of acid to add to the water. You can use my pool CYA calculator to determine exactly how much to add.

Step two: Check the chlorine you use

Some sanitizers known as stabilized chlorine, such as dichlor and trichlor, come with CYA already added. So be sure to check your chlorine to make sure you aren’t adding any more CYA accidentally.

Step three: Mix the CYA with water

Mix the CYA in a 5-gallon bucket with water, and make sure to add the water to the CYA and not the other way around! When handling CYA, read all of the directions and wear acid-resistant gloves and eye protection.

Step four: Pour the CYA into your pool or skimmer

After the solution is mixed, pour it into your skimmer. Then allow your pump to run for about 24-48 hours to circulate the acid. Repeat the process if needed.

Here’s a good video on how to add cyanuric acid to your pool.

How to Lower CYA Levels

Lowering the level of CYA in your pool is a bit more complicated. In some cases, you may need to drain your pool. High CYA levels are not very harmful to swimmers, but it can damage the edges of the pool. In addition, more CYA in the pool will lessen the effects of chlorine which, in turn, can make your pool cloudy. The only thing that lowers high CYA levels is dilution, which means partially draining and refilling your pool. Here is the equipment you’ll need to do to reduce the CYA level of your pool.

  • Pool water testing kit
  • Garden hose
  • Cyanuric acid reducer
  • CYA (if needed to add more after draining)

Step one: Test the water

Like raising the level of CYA, the first step is to test the water and see where your levels are.

Step two: Determine how low the levels need to be dropped

If your readings are just a little high, there are cyanuric acid reducers that you can use. Follow all safety information and warnings for any product you buy. However, if they are at a higher ppm, you may also need to dilute the water.

Step three: Drain some pool water and refill with the hose

After determining how high the levels are, drain the excess percentage of water. For example, if the CYA level is 20 percent higher than it should be, you will need to drain 20 percent of your pool. Then refill the pool with a garden hose.

Step four: Allow the pump to mix the water

After adding the new water, allow the pump to mix the old pool water and fresh water for about 8 hours.

Step five: Test the water again

The final step is to test the water again to be sure the levels are correct. If the level is still too high, repeat the process. If it is too low after draining, then add some more CYA.

If your levels are really high, you may have to fully drain and refill your pool.

What Are Cyanuric Acid Reducers?

CYA reducers are new to the market, and many pool owners use them as an alternative to draining the pool. They will attach to cyanuric acid at the molecular level and break down the chemical.

Bringing your water to the ideal CYA level with only CYA reducers can be tough. Generally, if cyanuric levels are too high, the best method is to use a CYA reducer to remove some CYA and dilute the water afterward.

Since CYA reducers are a new product, there has not been much research on their overall effectiveness. But the consensus from pool owners is that the reducers work and can save a lot of time and money from draining and refilling the pool.

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How to Maintain the Correct Cyanuric Acid Levels

The best recommendation I can give you to maintain your CYA levels is to test the water frequently. You can use standard testing strips to test the water and calculate the CYA levels. It is good to check this, especially after heavy rainfall. Still, I recommend keeping track of the levels at least once a week. The ideal CYA levels are around 40-50 ppm.

Cyanuric Acid Safety

Here are some of my top safety precautions for handling cyanuric acid:

  1. Wear proper safety equipment. When working with pool chemicals, you should always wear appropriate PPE gear. Wear long sleeves, long pants, closed-toe shoes, gloves, and goggles. Cyanuric acid is not as hazardous as other pool chemicals because it is a pretty weak substance. But it would be best if you still took the proper precautions.
  2. Rinse off any contact with CYA. If the product makes contact with your skin or eyes, wash them immediately, as prolonged interaction can cause irritation. Call a doctor immediately if you experience any serious irritation or reactions to the chemical.
  3. Don’t use it for hot tubs. Warm water is often a breeding ground for all sorts of bacteria and other unwanted substances. Since CYA reduces the effectiveness of chlorine, which hot tubs desperately need, try to avoid using CYA if possible.
  4. Don’t use it for heavy-traffic pools. Similarly, pools with high use, such as public pools, should use little to no CYA. You want the chlorine to work as efficiently as possible when a lot of germs and bacteria are introduced to the pool water.

Government Regulations and Limits for CYA Levels

The CDC (Centers for Disease Control and Prevention) recommends keeping your pool pH at 7.2–7.8 and free chlorine at a minimum of 2 ppm if you use CYA. They don’t have recommended levels of CYA for private pools.

Your local and state government may also have guidance for CYA levels; you will need to check on your local public health department website for that up-to-date information.

The Bottom Line on CYA and Your Pool

One of the main pillars of pool care is keeping your levels balanced. This balance means maintaining optimal pH, sanitizer, and CYA. Chlorine is vulnerable to the sun, and CYA can protect it, but the trade-off is your chlorine will be less efficient.

If CYA levels in your pool are too low, you’ll need to use a lot of chlorine to adjust. If they’re too high, you will need to dilute them.

Striking the right balance is essential for CYA to work correctly and keep your pool looking fresh throughout the summer season.

Questions about cyanuric acid? Let me know; I’m always happy to help.

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