How to Lower High Cyanuric Acid in Pool

How to Lower High Cyanuric Acid in Pool

Chlorine will break down and degrade fast when exposed to the sun’s UV rays. This makes it vital to use cyanuric acid (CYA) to stabilize it. However, despite its effectiveness at stabilizing chlorine, too much CYA in pool water can be problematic.

High cyanuric acid levels reduce the effectiveness of chlorine and hence leaving the pool water unsanitized. Additionally, you are more likely to get inaccurate alkalinity readings, making it hard to keep pool chemistry in balance.

As a pool owner, it is essential to understand the optimal levels of CYA to maintain, how to test it and how to lower it in case there is too much of it in the water.

What’s the Optimal Level of Cyanuric Acid? 

The optimal levels of CYA for a swimming pool that uses a chlorine-based sanitization system is between 30 and 50 ppm (parts per million). If you use a saltwater system, the levels should be between 60 and 80 ppm.

Anything higher than this will still prevent the chlorine from degrading under the sun, but it will render it ineffective in cleaning the pool water. Therefore, the higher the CYA level, the more chlorine you need to add to ensure effective pool sanitization.

It is important to note that adding CYA beyond the recommended levels does not increase the effectiveness of your pool’s sanitizer.

How to Test Cyanuric Acid? 

It is always a good idea to test the CYA levels in your pool when doing routine tests for things like pH and alkalinity levels. However, it is even more critical to test for it when you notice string chlorine smells from your pool, as this is one of the signs of high CYA levels.

You can test using regular pool test strips like the JNW Direct Pool and Spa Test Strips or a digital test kit like the LaMotte 2056 ColorQ Pro 7.

When testing for cyanuric acid, it is best to take at least two samples: one from the deep end and the other from the shallow end. Also, ensure that you collect the samples several inches deep and avoid the surface water as it will not give you accurate results.

2 Methods for Lowering High Cyanuric Acid in Pool 

Although high CYA levels in pool water can be problematic, there are no quick and easy fixes for the problem. However, here are two effective methods you can use to deal with the situation.

Method 1: Dilute Your Water

Like when dealing with high chlorine levels, diluting your water is one of the simplest and most effective ways of lowering cyanuric acid. Although there is no exact science on how much water you need to dilute, the logical thing to do is replace 10% of the water if the CYA levels are higher by 10%.


Step 1 – Test CYA Level

Before you start draining and replacing your pool water, you first need to determine the specific CYA levels in the pool by conducting tests.

Step 2 – Drain the Pool

Once you figure out the CYA levels, you should calculate the percentage of water you need to drain and pump it out. If the levels are a little over 80 ppm, you should partially drain the water and replace it with fresh water.

However, if you have anything over 100 ppm, it is better to drain the pool entirely and fill it up again, then you can add the right amount of CYA and other pool chemicals.

Step 3 – Refill Pool

Once the pool is wholly or partially drained, you should add clean water and keep a close watch to prevent overfilling.

Step 4 – Retest CYA Again

After refilling the pool, you have to wait for at least 3 hours before testing the CYA levels again. If the level is still higher than optimal, you should repeat the process one more time.

Method 2: Use a Cyanuric Acid Reducer

If your CYA levels are incredibly higher, it is always better to start by adding a reducer before diluting the water. However, it is crucial to make sure you do not use other pool chemicals like algaecide for at least 7 days before adding the CYA reducer to ensure maximum effectiveness.


Step 1 – Test the Pool Chemistry

Start by testing your pool’s chemistry at least once a day before and repeat on the day you plan to add the CYA reducer. You need to make sure the pH level is 7.2 to 7.6, the chlorine level is 1 to 3 ppm, and the alkalinity is 80 to 120 ppm before adding this chemical.

Step 2 – Determine How Much Reducer to Use

Next, you will need to figure out how much CYA reducer to use. If you have a 25,000-gallon pool, you will need around 8 ounces of the reducer.

Step 3 – Mix and Pour the Reducer

The next step is to mix the reducer with water. Check the manufacturer direction for the exact amount of water you need. Once the mixture is ready, pour it on the pool’s perimeter as close to the return jets as possible for faster distribution.

Step 4 – Wait for a Week and Retest the CYA Level

When using a CYA reducer, you have to wait for at least a week before testing the levels again. However, the chemical is not harsh, and so the pool is still usable as you wait.

Bottom Line 

Cyanuric acid is vital for ensuring chlorine effectively sanitizes pool water by preventing it from breaking down under the sun. However, too much of it causes more harm than good.

The good news is that you can reduce the levels quickly by diluting your pool water or with a CYA reducer. However, it is better to keep track of the levels through regular measurements to save you the hassle of trying to lower them.

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