Cyanuric Acid (CYA)

What is Cyanuric acid?

Cyanuric acid (CYA) is in powder form and is often labeled as sunscreen or sunblock. CYA works by binding to the free chlorine in your pool which protects it from being killed off by the sun’s UV light. Remember, CYA will extend the life of your pool chlorine. So, if you use liquid chlorine with CYA, then the amount of chlorine you need to keep the water safe is reduced. More importantly, this saves you a lot of money.

Remember that high CYA levels in your pool are dangerous. It is important that your CYA levels are checked regularly so that the free chlorine remains effective and can keep the water safe for swimmers.

Here’s how high CYA levels can impact chlorine in a pool.

Chlorine Stabilization: Cyanuric acid acts as a chlorine stabilizer, protecting chlorine molecules from being broken down by UV sunlight. This is especially important in outdoor pools exposed to direct sunlight because it helps chlorine last longer in the water.

Reduced Chlorine Activity: While CYA stabilizes chlorine, it can also reduce the chlorine’s activity. As CYA levels increase, the effectiveness of free chlorine in killing bacteria and algae diminishes. This means that even if you have what appears to be a sufficient amount of chlorine (as measured by free chlorine levels), it may not be as effective in sanitizing the pool when CYA levels are high.

Higher Chlorine Demand: Pools with high CYA levels often require higher chlorine levels to maintain adequate sanitation. This is because a greater amount of free chlorine is needed to overcome the stabilizing effect of CYA and effectively kill contaminants.

Chlorine Lock: When CYA levels become excessively high (above recommended levels), it can lead to a condition known as “chlorine lock” or “stabilizer lock.” In this situation, the chlorine becomes less active and less effective in sanitizing the pool. This can result in persistent algae growth and water quality issues.

Reduced Responsiveness to Shock Treatments: High CYA levels can make it more challenging to eliminate pool problems, such as algae outbreaks or chloramine buildup, even with shock treatments. Shock treatments may not be as effective at breaking down contaminants in the presence of excessive CYA.

To address high CYA levels and maintain proper chlorine effectiveness.

Regularly test your pool water for CYA levels. The recommended CYA level for most outdoor pools is typically in the range of 30 to 50 ppm (parts per million), but this can vary depending on your specific pool and climate.

If CYA levels are too high, partially draining and diluting the pool water with fresh water can help reduce CYA levels. Also, consider using non-stabilized chlorine products periodically, such as liquid chlorine or calcium hypochlorite shock, to help reduce the buildup of CYA.

Be diligent about maintaining proper water balance and regular pool maintenance to minimize the impact of high CYA levels on chlorine effectiveness.

It’s important to strike a balance between using CYA to protect chlorine from sunlight and ensuring that your pool water remains properly sanitized. Monitoring CYA levels and adjusting them as needed is essential for maintaining a safe and clean swimming pool

Chlorine Tablets are full of CYA

Using chlorine tablets continually will increase the CYA levels in your pool. This is because they contain around 55% of CYA. So each tablet you add to the pool will increase the CYA level. Remember, if you use these tablets constantly then your CYA level will get too high. And, once the CYA level get too high, it can cause staining, cloudy water and make the pool water unsafe.

chlorine tablets

Chlorine tablets contain 52% CYA. Continued use will cause the CYA levels to increase.

Cyanuric acid reducer

These days, there are a lot of products that claim to reduce the CYA levels in your water. Most of these products are made by respected brands in the industry. So if you have high CYA and don’t want to drain any of your water then these products may be worth a try. On the other hand, draining part of your pool water and refilling will also achieve the same result.

Testing the CYA levels in your pool

You can test your CYA levels in two ways. First, you can use a pool water testing strip as shown in the video. Second, you can take a water sample to your local pool shop for testing. Generally, they will help you with this test and also offer free advice. You can increase the CYA levels in your pool by adding CYA. Remember, if your pool runs only on liquid chlorine then proper CYA levels are vital. This is because if your CYA levels are low then your chlorine use will increase substantially.

High CYA can lead to purple staining

As the image below shows, very high cyanuric acid levels, when combined with copper, can lead to purple staining on the pool walls and floor. The picture shows how this can look in a fibreglass pool. This type of staining is very uncommon. If your CYA levels are correct then it is very unlikely that you will ever see staining like this.

It is caused when copper sulphate from algaecides combines with very high CYA levels in the pool. As they interact with each other, they leave a stubborn purple stain on the walls of the pool. If you have this type of staining and would like it removed there is more information about that online.

staining from CYA

This pool had excessive CYA levels so when copper-based algaecide was added the walls turned purple.cyanuric acidbgbbbbbbbbbbbbbbbbbbbb