How to Lower Cyanuric Acid in Your Pool (in 4 Easy Steps)

Cyanuric acid (CYA) is one of the lesser-known chemicals in the pool industry. However, it plays one of the most important roles in maintaining adequate chlorine levels. CYA binds to the chlorine in your pool and prevents it from evaporating too quickly.

Unfortunately, excessively high cyanuric acid levels can stop chlorine from working, which means knowing how to lower it is essential for maintaining a healthy pool environment.

To lower the cyanuric acid in your pool, follow these step-by-step instructions:

1. Test the cyanuric acid
2. Drain the pool up to ⅓ of the way
3. Refill the pool with water
4. Test the CYA and see if you need to drain it again

In this article, I’ll explain why your pool’s CYA shouldn’t be too high, how you can correct it, and provide a few tips I learned during my years as a pool technician that will help you reduce cyanuric acid without draining the pool (using a new, non-toxic chemical).

1. Test Your Pool’s Cyanuric Acid Levels

Before draining or treating your pool for cyanuric acid issues, it’s important to test the water.

Your pool should have a CYA level between 40 to 80, though some experts recommend letting the CYA get up to 95 before draining the pool.

Too much cyanuric acid ruins the chlorine in the water, regardless of how much you add.

You can test the cyanuric acid with test strips or liquid drops. Most pool stores will test for CYA, but not too many mobile pool services do the same.

Here are the pros and cons of using strips vs. using drops:

• Cyanuric acid test strips are quick, but they can be difficult to read. The colors vary from bright yellow to pink. Unfortunately, most CYA test strips don’t show anything over 100ppm. Your pool could have a 300ppm CYA reading, but you wouldn’t know it if you used the test strips. Nevertheless, they’re budget-friendly and easy to use.
• Cyanuric acid liquid drop tests are much more accurate, but they tend to cost more than the strips. Most CYA liquid drops come in multipacks with several other tests. They’re much more accurate, and they don’t expire nearly as quickly as the strips. Furthermore, they provide higher readings.

The Taylor Swimming Pool Test Kit includes everything you need to test your swimming pool, including a cyanuric acid tester.

It includes a helpful chart that tells you when you need to add cyanuric acid or if you need to drain the pool to reduce the levels. (I’ll show you another solution that doesn’t require draining later in the post.)

2. Drain the Pool ⅓ of the Way To The Bottom

The most effective way to reduce your pool’s stabilizer is to drain it.

Some people can get away with only draining a foot or so in their pool. On the other hand, you might need to drain it multiple times to achieve the desired results.

Pro-tip: You should never drain a swimming pool more than ⅓. If you drain it more than that, you’re risking permanent damage to the liner.

To drain your swimming pool, follow these steps:

1. Turn off the pump to prevent it from sucking air into the system.
2. Place a sump pump into the swimming pool.
3. Plug the sump pump into the closest electrical outlet and attach a hose to the other end.
4. Place the hose wherever you want the water to drain. (Contact your city to know where you’re allowed to drain the water since pools often contain thousands of gallons).

If you need a sump pump, the Superior Pump Pool Sump Pump is an excellent choice because it includes a 10-foot cable and a powerful ¼-HP motor. You can use it to drain several thousands of gallons per hour, and it won’t crack or tear your pool’s liner or gunite. You can choose a variant with a bigger motor if you need to.

Pro-tip: Keep an eye on the pool while it’s draining. Too much water loss can cause damage to vinyl, gunite, plaster, and pebbles in your pool. I often tell people to drain one foot at a time. Drain a foot of water, refill it, test the CYA levels, and repeat the process. This method might seem tedious, but it’s the safest way to drain and fill a swimming pool.

3. Refill the Pool With Fresh Water

To refill the pool, pour hose water into the pool until the water is above the skimmer basket.

Don’t turn on the pump until the water is higher than the highest inlet. Remember to prime your pump when you’re done filling the pool. You should also open the filter’s air relief valve to get rid of excess air bubbles while the pump is running.

Hose water, well water, and rainwater shouldn’t have any cyanuric acid. Therefore, draining your current water and filling it with water from one of these sources will quickly lower the conditioner levels in the pool.

Pro-tip: I suggest avoiding this process during droughts and water shortages since you’ll likely require at least 2,000 gallons of water.

4. Retest the Cyanuric Acid Levels in the Pool

When you’re done refilling the swimming pool, it’s time to check the CYA levels again. Know that you’ll likely have to drain it multiple times if there was a ton of cyanuric acid in the water to begin with. For example, a CYA reading of 150 will drop to 100 after draining the pool ⅓ of the way, which is still above the recommended range.

Another suggestion is to remove the pool cover and let the sun’s heat evaporate the water. When you add hose water to the pool, it’ll dilute the cyanuric acid.

This method takes much longer than draining, but it’s actually the way most pool owners maintain the CYA levels without knowing it. Rainwater can also naturally dilute the stabilizer, so you might consider leaving the cover off when it rains.

How Do I Lower the Cyanuric Acid In My Pool Without Draining It?

To lower the cyanuric acid in your pool without draining it, follow this process:

1. Test the water and keep the chemicals within their optimal ranges. The chlorine should be between 1ppm to 5ppm, the pH should be between 7.2 to 7.8, and the alkalinity should be between 80 to 120. If any of these ranges deviate, this process won’t work, and you’ll have to drain and refill the pool.
2. Pour Bio-Active Pool Stabilizer Reducer into the skimmer after removing the basket. Turn on the pump and make sure it runs as much as possible throughout the next week. This cyanuric acid reducer needs constant circulation to work, as it has to come into contact with as much of the water as possible.
3. Don’t use any chemicals other than chlorine, soda ash, muriatic acid, and baking soda during the treatment process. Most other pool chemicals disrupt the process. Bio-Active is extremely sensitive, so your pool has to stay within the recommended parameters for it to work properly.
4. Keep the swimming pool above 65 degrees Fahrenheit (18.3 Celsius). Bio-Active CYA Reducer uses natural ingredients that don’t work in cold water. You have to keep the pool warm enough. Learn how pools are heated to ensure the water never dips below the required temperature range throughout the process.
5. Remove algae blooms and cloudiness as quickly as possible. Algae can interfere with the stabilizer reduction process. Too much algae, total dissolved solids, and other debris will make it impossible to see results.

This method takes about 7 to 10 days. Bio-Active is one of the most finicky pool chemicals, but using it is the only way to reduce the cyanuric acid without draining the water. It can drop the CYA by up to 50%, bringing it back to the recommended range between 40 to 80.

Note: If your pool has extremely high cyanuric acid levels, you’ll likely have to use two or three bags of Bio-Active. For example, a CYA reading of 300 will drop to 150 after one bag and 75 after two bags.

If you want to learn more about using Bio-Active to reduce your swimming pool’s stabilizer, watch this Leslie’s Pool Supplies video on YouTube:

What Causes Cyanuric Acid to Be High in a Pool?

Cyanuric acid is high in a pool when there are too many chlorine tablets, someone added too much pool conditioner, or stabilizer-packed chemicals are added to the pool. Your pool’s CYA shouldn’t go above 100ppm since it’s too high to let the chlorine work. It’ll prevent chlorine evaporation, but the chlorine won’t be able to sanitize the water.

High cyanuric acid levels seem to creep up out of nowhere. Pool owners often don’t know they’re approaching dangerous CYA levels until it’s too late.

Your pool’s chlorine will be effective when the cyanuric acid reaches 90ppm, but 100ppm renders it mostly useless. There are a few things that contribute to high CYA levels, all of which should be monitored and maintained.

Here’s what increases the cyanuric acid in your pool:

• Most chlorine tablets contain cyanuric acid. Look for a label that mentions chlorine stabilizer, CYA, or pool conditioner. All of these turns mean the same thing: there’s a lot of cyanuric acid in the tablets. The CYA in the tablets passively increases the levels to a healthy range, but a lack of dilution can elevate the CYA too much.
• The pool conditioner increases the swimming pool’s cyanuric acid. Conditioner is sold in liquid form or granular form. Make sure you don’t add too much CYA to the pool at a time, or you’ll quickly exceed the recommended range. I suggest getting the CYA to 40 and letting the chlorine tablets do the rest.
• Some other pool chemicals contain trace amounts of cyanuric acid. Check the ingredients of anything that goes in the water to ensure there’s no stabilizer. If there is, it will likely increase your pool’s cyanuric acid. While CYA is very necessary for all swimming pools, it shouldn’t be added to everything you dump into the water.

Pool owners often overcompensate for the lack of chlorine activity by pouring more shock or liquid chlorine into the pool.

You can add loads of chlorine into the water without it doing anything other than creating a hazardous swimming environment. Therefore, you should make sure you lower your chlorine levels to 1ppm to 5ppm when swimming or using CYA reducers.

Is It Safe To Swim in a Pool With High Cyanuric Acid?

It’s safe to swim in a pool with high cyanuric acid, but it can be mildly irritating to the eyes. However, diluted cyanuric acid doesn’t cause itchiness or irritation, so you likely won’t feel anything. Too much CYA can render your chlorine useless, so there could be dangerous algae blooms worth looking into.

Keep these things in mind before swimming in a pool with high cyanuric acid:

• Most cyanuric acid treatments recommend waiting 20 minutes before swimming. Test the pool once the liquid or powder solution dissolves to know if you have high CYA. The reading will always be much higher if you test a concentrated portion of cyanuric acid in the swimming pool.
• It’s important to know how to backwash your filter after using a cyanuric acid reducer or increaser. Both of these treatments can get trapped in the filter, and they need to be removed if they do get caught. Backwashing the filter gets rid of the excess cyanuric acid, freeing your chlorine to be much more effective.
• Too much cyanuric acid in the pool can cause algae blooms because it limits chlorine’s potency. While CYA might not directly harm your health, the algae floating in the water and stuck in the porous liner could be dangerous. Clear up all algae blooms and cloudiness before swimming in the water.
• Cyanuric acid can lower the pool’s pH and alkalinity, making it dangerous for swimming. Test the pool’s pH, alkalinity, and chlorine before jumping into the water. Remember to use soda ash and baking soda to increase the pH and alkalinity. Spiking the chlorine over 5ppm for too long can cause skin and eye irritation.

Cyanuric acid isn’t directly dangerous to swim in when it’s diluted in a pool. However, it can cause multiple unwanted side effects that can lead to unsettling, hazard-ridden swimming pools. Always check and maintain your pool’s CYA before taking a dip.