Drain and refill. That's it.

Partial drain and refill is the only reliable way to lower CYA. Those “CYA reducer” chemicals? Overpriced, slow, and barely work. Don’t waste your money.

Here’s the deal: Cyanuric acid (stabilizer) doesn’t evaporate or break down naturally. It only leaves when you physically remove the water. So you need to drain a portion of your pool and refill with fresh water.

How much to drain: Test your current CYA level and figure out what you want it to be (ideally 30-50 ppm for most pools). For example, if you’re at 100 ppm and want 40 ppm, you need to replace about 60% of the water. Drain, refill, test again, repeat if needed.

Safety note: Don’t drain a concrete or gunite pool completely—the ground pressure can crack it or pop it out of the ground. Stick to draining a third or half at a time. For vinyl or fiberglass, partial drains are fine, but check the manufacturer’s limits.

One last thing: stop adding more tablets or shock with stabilizer until you fix the CYA. You’re just digging a deeper hole.