Cyanuric Acid

Modified on Fri, 17 May at 3:07 PM

Cyanuric Acid (CYA) is a chemical compound that is often used in pool water chemistry as a stabilizer for chlorine. Think of it as a shield to protect chlorine from being consumed by the sun.

The recommended range for CYA in a swimming pool is between 30 and 50 ppm. If the CYA level is too low, the chlorine can be quickly degraded by sunlight, which can result in inadequate water sanitation and increased risk of algae growth. If the CYA is too high it can over-protect your chlorine to the point that it can't do it's job.

Regular monitoring of CYA levels is important to maintain proper water sanitation and prevent issues with pool water quality.

What Happens when my CYA is really high?

If your CYA levels are too high, Crystal Water Monitor will most likely tell you that your ORP is too low and that you should add chlorine. This is because the ORP measures the activity of your chlorine and it's all bound-up by the CYA rendering it ineffective. In this scenario you should target a higher than normal free chlorine level to account for the ratio of your chlorine that is rendered ineffective by the CYA.

Here's a chart showing the minimum free chlorine target considering increasing CYA levels:

You can find the target free chlorine level in the Crystal Water Monitor app when you're being asked to raise your ORP / add a chlorine:

Lowering CYA via Dilution

Reduce the CYA of your water by draining one foot of water and introducing new water. Be sure to only drain your pool one foot, refill that one foot, and then repeat this process as many times as necessary to reduce your CYA levels. DO NOT DRAIN YOUR POOL MORE THAN 1 FOOT AT A TIME OR YOU RISK DAMAGING YOUR POOL.

Lowering CYA via CYA Reducing Chemicals

We've seen mixed results with CYA reducing chemicals but if you think they're worth a try feel free to do so.

Raising CYA

Many pool sanitizers contain CYA like granular dichlor and trichlor tablets. To raise the CYA level, pool owners can also add CYA directly to the pool water, usually in the form of granules or tablets. It is important to note that CYA does not dissipate from the water over time, so if the CYA level becomes too high, it may be necessary to partially drain and refill the pool to lower the CYA level.

Note: When your CYA levels exceed the recommended range, you will need additional sanitizer to keep your water properly sanitized.    Free Chlorine levels should be 7.5% of your CYA levels for effective sanitization.