5 Things to Know About Lowering Cyanuric Acid in Your Pool

Partial drain and refill is the only reliable way to lower CYA. Cyanuric acid does not evaporate or break down easily. No chemical or filter media will remove it in meaningful amounts.

CYA accumulates from stabilized chlorine sources. Tablets and shock containing stabilizer add CYA over time. If you use these regularly, expect levels to rise.

Calculate how much water to replace based on your CYA level. Measure current CYA and set a target of 30–50 ppm for outdoor pools. If you are over 100 ppm, plan to replace 50–70% of the water.

Do the drain and refill in stages over a few days. This prevents ground pressure or liner damage. You do not need to drain the entire pool at once.

Lower CYA makes your chlorine more effective. High CYA reduces chlorine’s ability to sanitize. Draining and refilling is a hassle, but your chlorine will work properly afterward.