3 Ways to Lower High Cyanuric Acid (CYA) in a Pool

Partial drain and refill This is the only reliable fix. Drain 30–50% of the pool, refill with fresh water, and test again. Repeat if needed. It works because every gallon you remove takes CYA with it.

Reverse osmosis filtration A truck filters the water and removes CYA without draining. It costs $400–$800 depending on pool size. This is a good option if you have water restrictions or want to avoid draining.

Bio-based CYA reducers Products like Bio-Active use bacteria to eat CYA. They work slowly over weeks and require constant monitoring and aeration. Only use this if you are patient and not in a hurry.