Cyanuric acid (CYA), also known as chlorine stabilizer or pool conditioner, is a chemical that helps stabilize the chlorine in your pool. It protects your chlorine from breaking down under the sun’s UV rays. The right levels of cyanuric acid help your chlorine last longer, which means your sanitizer can continue to kill bacteria, contaminants, and algae.
But having too much or too little cyanuric acid in your pool can reduce your chlorine’s effectiveness and even damage your equipment. Here’s everything you need to know about how cyanuric acid works with chlorine and how to raise or lower your cyanuric acid levels.
You can watch the quick video tutorial below. Or keep reading for the step-by-step guide on how to adjust your cyanuric acid levels.
How Does Cyanuric Acid Work in a Pool?
Cyanuric acid, or chlorine stabilizer, reduces the amount of chlorine that’s lost from the sun’s UV rays. It helps your chlorine last longer, which means it sanitizes your pool water longer.
If you have an outdoor pool without stabilizer, your chlorine will dissipate in a few hours, leaving your pool unprotected and unsanitized. Within just 17 minutes of exposure to UV rays, half of your chlorine will be gone. Adding cyanuric acid helps your chlorine last 3-5 times longer.
Pools with very low or no cyanuric acid will have significant chlorine demand or a consistent inability to maintain chlorine levels. Unstabilized chlorine (i.e. chlorine without cyanuric acid) is destroyed by UV rays very quickly.
Because cyanuric acid protects chlorine from the sun’s harmful UV rays, CYA is recommended for outdoor pools only. This is also because cyanuric acid stays in a pool for a long time, even after the water evaporates. Always check your cyanuric acid levels before adding more stabilizer to your water.
What Are the Right Cyanuric Acid Levels?
The ideal range for cyanuric acid is between 30 and 50 ppm. Maintaining the right balance between cyanuric acid and chlorine is crucial for a sanitized pool. Too much cyanuric acid and your chlorine’s effectiveness decreases. Too little cyanuric acid and your chlorine will break down under the sun’s UV rays.
Aim to keep free chlorine levels at 7.5 percent of cyanuric acid levels. If your pool has CYA levels at 50 ppm, you’ll need to keep your free chlorine levels at 3 ppm to effectively sanitize your water. In general, your free chlorine should be between 1 ppm and 3 ppm.
Remember, more cyanuric acid does not mean more protection from the sun. If your CYA levels are over 50 ppm, you may experience algae growth or cloudy pool water. That’s because your chlorine’s effectiveness is reduced. If your CYA levels are 100 ppm or higher, you may not even be able to get an accurate reading on a test strip. Consider taking a sample to a pool supply store or using a test kit that measures up to 300 ppm.
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What Causes High Cyanuric Acid Levels?
Many chlorine products, like trichlor or dichlor granules or tablets, already include cyanuric acid. These are known as stabilized chlorine products. So every time you add chlorine to your pool, you’re adding CYA. On the other hand, unstabilized chlorine, like liquid chlorine, does not contain cyanuric acid. You can learn more about the difference between stabilized and unstabilized chlorine here.
If you do need to add cyanuric acid to your pool, it’s sold as a separate product, which is often called stabilizer or conditioner. Here is the CYA we recommend:
Cyanuric Acid (Chlorine Stabilizer) for Pools
Keep your chlorine from being burned off too quickly by the sun’s UV rays. CYA will help you keep a better chlorine reading in your pool.
But be careful how much extra CYA you add to your water. It’s very hard to lower your CYA levels if they’re too high. And cyanuric acid does not evaporate or break down like chlorine, so it will stay in your pool water. It can even hang around in your filtration system and pool plaster.
How to Lower Cyanuric Acid in Your Pool
The only effective way to lower your cyanuric acid levels is to partially drain your pool and refill it with fresh water. If you think your cyanuric acid is too high, the first step is to stop adding more CYA to your pool before diluting your water.
1. Test Your Pool Water
Test your pool water to see if your cyanuric acid levels are between 30 and 50 ppm. Some test strips will measure CYA levels, but a liquid test kit will give you a more accurate reading. You can also bring a water sample to your local pool store for testing. Most tests don’t register cyanuric acid levels above 100 ppm, so multiple tests may be needed as you attempt to bring your levels down. You may also want to look for a test kit capable of measuring CYA at 300 ppm.
2. Stop Using Stabilized Chlorine
Check to see whether you’re using stabilized chlorine, which already contains small amounts of cyanuric acid. If you see these chemicals listed on the label, your chlorine contains CYA:
- potassium dichloroisocyanurate
- sodium dichloroisocyanurate
- trichloroisocyanurate
If you find this is the issue, switch to chlorine without cyanuric acid to prevent your high CYA levels from getting worse.
3. Dilute Your Pool Water
If your cyanuric acid levels are very high, you must dilute your pool water. Partially drain some of your pool water by using a manual vacuum on your filter’s waste setting. Then refill your pool with fresh water. In general, if your cyanuric acid levels are 10% too high, you’ll want to remove and replace about 10% of your pool water. Be aware that cyanuric acid can hang around in your filtration system, so if you have extremely high levels of CYA, you may want to backwash or change your filter.
4. Circulate and Retest Your Cyanuric Acid Levels
Run your pump for a few hours to circulate the freshwater. Then retest your cyanuric acid levels again. If they are still too high, repeat the process of diluting your pool water.
Do Cyanuric Acid Reducers Work?
Cyanuric acid reducers have mixed results. These products claim to reduce cyanuric acid levels by 50%. But many customers have reported that it did not reduce their CYA levels at all.
Cyanuric acid reducers are biologically based, so they work slowly. It can take a week or more to reduce your CYA levels. And the chlorine in your pool can destroy the helpful bacteria found in a cyanuric acid reducer. You’ll need to keep your chlorine levels low (around 1 ppm) when using this product.
Finally, cyanuric acid reducers are not cheap. You could partially drain and refill your pool for roughly the same cost, depending on the water utility costs in your area. If you cannot dilute your pool water because of drought conditions or municipality restrictions, it might be worth trying a cyanuric acid reducer.
How to Raise Cyanuric Acid in Your Pool
If you’re using stabilized chlorine (like dichlor or trichlor), you probably won’t need to add any extra cyanuric acid to your pool water. However, if you do need to add CYA to your pool separately from your chlorine, you’ll likely only need to add it once or twice per year. Remember, cyanuric acid does not break down in the water and can stay in your pool for a long time.
Because CYA is an acid, it can damage your filter and your pool, especially if you have a vinyl liner. Here is the safe way to add cyanuric acid, also known as stabilizer or conditioner, to your pool.
You’ll need the following supplies:
- Cyanuric acid (a.k.a. conditioner or stabilizer)
- A 5-gallon bucket
- Safety goggles
- Acid-resistant gloves
- Warm water
To add cyanuric acid to your pool:
- Fill the bucket at least halfway with warm water.
- Put on your goggles and gloves.
- Add a dose of cyanuric acid to the bucket. Check the product instructions for the right dose based on your pool size. As a general rule, you’ll need to add 13 ounces of cyanuric acid to gain 10 ppm of CYA in a 10,000-gallon pool. Remember, the proper levels for CYA are 30 to 50 ppm.
- Pour the contents of the bucket directly into your skimmer.
- Run your pool pump for at least a few hours after. Letting the pump run is like stirring the solution into your pool, just without having to use an enormous spoon.
Note: Some packages of cyanuric acid say to add the chemical directly to the skimmer without first combining it with water. Always read the manufacturer’s instructions before using.
How to Maintain the Right Cyanuric Acid Levels
To keep your cyanuric acid levels balanced, regularly test your pool water — especially if you’re using stabilized chlorine or you tend to have problems with high CYA.
Use test strips that measure cyanuric acid and check your water chemistry once a week. Be sure to test your pool water after a rainstorm, as that will dilute your water and lower your CYA levels.
Remember, your free chlorine levels should be about 7.5 percent of your CYA levels. That means if your pool has 50 ppm of cyanuric acid, you’ll need to keep free chlorine at 3 ppm.
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A simple but effective liquid test kit for chlorine pools and hot tubs.
Frequently Asked Questions about Cyanuric Acid
Looking for more help with using cyanuric acid in your pool? Here are some common questions and answers.
Is Cyanuric Acid Harmful?
While cyanuric acid is technically an acid, it’s very different from other acids like muriatic acid. Cyanuric acid can dissolve in water and does not significantly affect your pH, alkalinity, or calcium hardness levels.
However, like other pool chemicals, it must be handled with caution. It can cause severe burns if it comes in contact with your skin or eyes. And its fumes can burn your nose or lungs if inhaled. Always wear acid-resistant rubber gloves, eye protection, long sleeve clothing, and handle CYA in a well-ventilated area.
Is There Another Name for Cyanuric Acid?
Cyanuric acid is called CYA, stabilizer, or conditioner. It is sold separately as conditioner and stabilizer or included in chlorine products like trichlor or dichlor.
Does Pool Shock Contain Cyanuric Acid?
Some pool shock, like dichlor shock, contain cyanuric acid. Unless you need to raise your CYA levels, use an unstabilized chlorine shock without CYA. We recommend using calcium hypochlorite shock, also known as cal-hypo shock.
Is Cyanuric Acid the Same as Baking Soda?
No, cyanuric acid and baking soda work in very different ways in your pool. Baking soda raises the total alkalinity in your pool. But baking soda does not protect or stabilize your chlorine, like cyanuric acid.
What Raises Cyanuric Acid in a Pool?
You can raise your cyanuric acid levels by adding a pool conditioner or stabilizer. If you do need to add cyanuric acid to your pool, here is the CYA we recommend:
Cyanuric Acid (Chlorine Stabilizer) for Pools
Keep your chlorine from being burned off too quickly by the sun’s UV rays. CYA will help you keep a better chlorine reading in your pool.
How Do High Cyanuric Acid Levels Affect a Pool?
When cyanuric acid levels get too high, it can hinder the effectiveness of your chlorine. If your chlorine test shows very or little chlorine even right after you’ve added it to the pool, your cyanuric acid may be too high. The only way to reduce CYA levels is to dilute your water by draining and refilling your pool.
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