How to Lower Cyanuric Acid in Pool (with 2 Simple Methods)

How To Lower Cyanuric Acid In Pool

Besides the obvious cost that comes with installing a swimming pool, you will also need to maintain it to keep it safe and protect your investment.

Maintaining a pool often requires the use of different chemicals like chlorine and cyanuric acid (CYA). Adding cyanuric acid ensures the chlorine will not lose its potency and will hence remain effective at cleaning the pool.

But, too much of the cyanuric acid can be detrimental. Hence, to keep your swimming pool in the best shape, you need to know how to lower it if it goes beyond the required levels.

What is Cyanuric Acid?

Cyanuric acid is also fondly referred to as chlorine stabilizer, and its primary function in a pool is to prevent the degradation of chlorine when it is exposed to elements like the sun. It comes in both granular and liquid form, and it is often added to the pool together with the chlorine.

Many chlorine tablets for swimming pools have at least 10% cyanuric acid in their formulation, and so when using them, you need not add more CYA.

When used correctly and kept at the right levels in your pool, CYA reduces the cost of maintaining your pool significantly by preventing chlorine loss.

Why Too Much Cyanuric Acid is a Bad Thing?

Typically, 30 to 50 ppm (parts per million) is considered the optimal amount of cyanuric acid in an outdoor swimming pool. However, this number can go up to 100 ppm, depending on how much direct sunlight it will get.

Anything above 100 ppm is considered too much for any pool and will have negative effects. Key among these adverse effects is that too much cyanuric acid will reduce the effectiveness of chlorine in keeping the pool clean. The cyanuric acid will bind the chlorine and make it harder for it to kill bacteria, algae, and other typical pool contaminants.

Also, too much of this compound in your swimming pool will hurt the overall balance of the water. High CYA levels can raise alkalinity levels, which in turn can cause damages to the pool’s plaster and pebbles and sometimes even lead to discoloration.

How to Test Cyanuric Acid Level

How to Test Cyanuric Acid Level


Testing the levels of cyanuric acid in your pool is vital to make sure the water chemistry is optimal for the safety of all users. And there are two main ways of testing cyanuric acid, which is by using test strips and doing the turbidity test.

Method 1: Using Test Strips

Then test strip method is the most straightforward way of testing for cyanuric acid levels in your swimming pool waters. All test strips will come with clear directions on what you need to do and how to read the color charts.

Overall, the test will entail submerging the test strips into the pool water for about 30 seconds to allow the color to change. You should then remove the strip from the water and compare the color on the strip with the provided chart to estimate the cyanuric acid levels.

Method 2: Using Turbidity Test

The turbidity test is more accurate when compared to using test strips, but it is also a more tedious test because, unlike the latter, it will entail taking a water sample.

When performing this test, you have to add the provided chemical reagent to the plastic vessel full of the pool water as per the manufacturer guidelines. You should then mix in the powder thoroughly by stirring or shaking and wait for about a minute for the chemical reaction to occur.

The reagent reacts with the cyanuric acid to create cloudiness/turbidity, and once this is done, you can transfer the liquid to the marked test tube that comes with the kit. On this tube, you will be able to read the exact cyanuric acid levels in the pool water.

Note: The turbidity test kit manufacturer will provide clear and step by step instructions for measuring the cyanuric acid levels, and so you need to read and follow them for accurate results.

How to Lower Cyanuric Acid in Pool

Lower Cyanuric Acid in Pool


After carrying out the tests and ascertaining that the cyanuric acid levels are higher than required, you need to lower it. Here there are also two main methods that you can use.

Method 1: Drain and Dilute

The most effective way to lower the CYA level is to drain and dilute your pool water. Note that if you have to drain more than a third of the pool’s water, you will need to first talk to a professional due to hydrostatic pressure concerns.

What You Will Need

  • Submersible pump
  • Test strips
  • Cyanuric acid

What You Need to Do

Step 1: Get a Pump

Because you will need a submersible pump to drain the pool, the first step should always be to get one.

Step 2: Measure the CYA Levels

Before you start diluting or draining your pool water, you first need to determine how much of it you will need to remove. Since this depends on the actual CYA levels in your water, you should first measure it using the test strips.

Step 3: Drain the Water

Once you know the levels of cyanuric acid in your water, you need to calculate the percentage you need to reduce. The CYA ratio that you will need to decrease in the water will also indicate the amount of water you need to remove from your pool. And once you have the right amount, you can then proceed to pump out the water.

For example, if you find that your CYA levels are around 100 ppm, you will need to reduce the level by 50% to least 50 ppm. This will also mean that you will need to remove 50% of the water in the pool and replace it with fresh water to dilute the CYA to the required level.

Step 4: Refill the Pool

The next step should be to add fresh water to the pool to replace what you have drained. Running one or more garden hoses into the bottom provides a fast and effective way of refilling the pool. Remember to keep a close eye on the water level as you fill-up the swimming pool to ensure water does not overflow.

Step 5: Measure the CYA levels Again

After filling up the water, you should wait for at least 3 hours and then measure the cyanuric acid levels one more time. If your calculations were correct when draining out the water, the CYA level should now be at the acceptable range of between 30 and 50 ppm.

If the level is okay, there is nothing more that you need to do. For lower ones, you will need to calculate how much more cyanuric acid you need and add it, and if it is still high, you need to drain and dilute again by following the steps above.

Note: If the CYA levels are too high (above 100 ppm), the best idea will be to empty the pool completely and then refill it again.

Method 2: Use Cyanuric Acid Reducer

Sometimes you do not have to go through the hassle of draining and refilling your pool because a commercial CYA reducer can be enough to get the levels down.

What You Will Need

  • Cyanuric acid reducer
  • Chlorine and CYA test strips

What You Need to Do

Step 1: Test Chlorine Levels

It is important to note that if your pool water has too much chlorine, the CYA reducers will not be useful for you. Hence before adding the reducer, you need to test the chlorine levels using a test strip, and if the levels are above 5.0 ppm, you should expose the water to the sun to reduce it.

Step 2: Add CYA Reducer

If the chlorine levels are okay (2 to 3 ppm), you can now add the cyanuric acid reducer. There are different types available in the market, but with most, you will need around 8 ounces of the product for every 10,000 gallons of pool water. Also, make sure you pour the reducer into the skimmer so that it can get to the filters quickly.

Step 3: Run the Filters

Next, you should run the pool filters for around 4 hours to allow the CYA reducer to cycle through the entire pool. After the 4 hours, you should now test the CYA levels to check whether the reducer has worked or not. In case it is still high, you can repeat the process one more time.


Cyanuric acid is a vital pool maintenance chemical as it helps slow down the deterioration of chlorine to minimize the maintenance cost. But, too much of it can reduce the effectiveness of the chlorine in cleaning your water.

The good news is that lowering the levels of this compound in your pool water is relatively easy. Once you measure and ascertain the levels are high, you can use either a cyanuric acid reducer or drain and dilute the water depending on the exact amounts of the CYA.