Stick to 30–50 ppm CYA for sunny pools.

Between 30 and 50 ppm.

Cyanuric acid (CYA) is basically sunscreen for your chlorine. Sunlight destroys free chlorine fast — like, half of it gone in an hour on a clear day. CYA slows that down. Without it, you’re pouring money and chemicals into a pool that never quite stays sanitized.

But more isn’t better. Above 50 ppm, the chlorine gets lazy. It’s still in the water, but it’s bound to CYA and less effective at killing algae and bacteria. You’ll end up needing way more chlorine to get the same punch. Below 30 ppm and you’re losing too much to the sun.

If your pool gets direct sun all day, aim for the higher end of that range — around 45–50 ppm. Test monthly and adjust with stabilizer or partial drain if needed.

Don’t fall for the “more is safer” trap. 30–50 is the sweet spot.