You can't fix high CYA without draining some water.

Not really.

Cyanuric acid doesn’t evaporate or break down on its own. It’s a stabilizer — it hangs around until you physically remove the water. There’s no magic chemical that zaps it.

You can do a partial drain and refill. That’s the standard fix. If you’re on a well or have water restrictions, that might be a pain, but it’s the only reliable method. Reverse osmosis filtration trucks can also do it (they filter out CYA without draining the whole pool), but that costs more and isn’t available everywhere.

Don’t buy any “CYA reducer” bottles. They don’t work. They either do nothing or mess with your chemistry in other ways.

If your CYA is only moderately high (like 60–80 ppm), switching to non-stabilized chlorine (plain liquid bleach or calcium hypochlorite) will at least stop it from climbing. But the existing level won’t drop unless you swap water.

You can keep swimming with moderately high CYA — just know you’ll need more chlorine to kill algae. Future you will thank you for doing a small drain now.