CYA Too High: What to Do
The only way to lower cyanuric acid (CYA) is to replace part of your pool water with fresh water — there is no chemical that removes it.
Safety first
- Never mix chemicals together.
- Always add the chemical to the water — never water to the chemical.
- Wear gloves and eye protection when handling pool/spa chemicals.
- Keep chemicals out of reach of children and pets.
- Always follow the product label — it overrides any guidance here.
Why CYA creeps up over time
Dichlor and trichlor are convenient — they both sanitize and add stabilizer in one step. The catch: every dose adds CYA, and CYA never breaks down on its own. Use either product all season and it's common to end up at 150-200+ ppm without ever intentionally adding stabilizer.
How to bring it back down
- Test your current CYA (or estimate from how much dichlor/trichlor you've used).
- Enter your current and target CYA into the Stabilizer (CYA) Calculator to get the dilution percentage.
- Drain that percentage of pool water and refill with fresh water.
- Re-test TA, CH, and FC after refilling — dilution lowers those too, so you'll likely need to re-dose them.
- Going forward, switch to liquid chlorine or cal-hypo (which don't add CYA) to keep it from climbing again.
Frequently asked questions
What does high CYA actually do?
CYA (cyanuric acid / stabilizer) shields chlorine from sunlight, but too much of it weakens chlorine's ability to kill algae and bacteria — so your usual FC level stops being effective.
Why did my CYA get so high in the first place?
Repeated use of dichlor or trichlor adds CYA every time (see our Chlorine Calculator for exact amounts). Over a season, CYA can creep well past 100 ppm without you adding it directly.
Is there a chemical that removes CYA?
No reliable one for home use. Dilution (replacing some pool water with fresh water) is the only practical fix.
How much water do I need to replace?
Use the dilution percentage from the Stabilizer (CYA) Calculator — it is based on your current and target CYA.