How to lower cyanuric acid (stabilizer) in a pool The short answer To lower cyanuric acid in a pool, replace some of the water: nothing you pour in removes stabilizer reliably. Draining a share and refilling with fresh water lowers it by the same share — going from 100 to 50 ppm takes half the water. The calculator below works it out for your pool. Then switch to liquid chlorine, so it stops climbing.
How much water to replace Stabilizer now
Cyanuric acid (CYA). It shields chlorine from the sun, so outdoor pools need some.
Stabilizer you want
Good range: 30–50 ppm.
Using stabilizer.
Type the size and your stabilizer reading.
Step by step Work out how much water to replace with the calculator on this page.
Drain that share and refill with fresh water. A big change is safer done in two or three rounds (a fully drained pool can float or crack).
Test again, then rebalance pH, alkalinity and chlorine.
Switch from tablets to liquid chlorine, so stabilizer stops building up.
The product label always wins — if it says something different, follow the label.
Why it happens Stabilizer only leaves with water. Trichlor tablets and dichlor shock add some every time you use them, so it keeps climbing in a pool that uses them.
Questions What should cyanuric acid be? 30–50 ppm in a chlorine pool, and 60–80 ppm in a salt pool.
Do cyanuric acid reducers work? Sometimes, and not in cold water. Replacing water is the one method that always works.
Why is high stabilizer a problem? It makes chlorine weaker: the more stabilizer, the more chlorine it takes to keep algae away.
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