Cyanuric acid (pool stabilizer)

Cyanuric acid (CYA), also called pool stabilizer or conditioner, binds with chlorine in pool water and protects it from UV degradation. Without CYA, sunlight destroys 90%+ of free chlorine within 2-3 hours of application. With proper CYA levels (30-50 ppm), chlorine half-life extends to days.

The trade-off: too much CYA reduces chlorine effectiveness ('chlorine lock'). At 100+ ppm CYA, free chlorine becomes meaningfully less effective at sanitizing the water — requiring higher chlorine doses to achieve the same effect. CYA doesn't break down naturally; it accumulates over time as stabilized chlorine products are added. The only way to reduce CYA is partial water replacement.

For pool service operators, CYA management is foundational. Common errors: relying on stabilized chlorine (trichlor, dichlor) for routine chlorination, which steadily increases CYA; failing to test CYA quarterly; not draining and replacing water when CYA exceeds 80 ppm. Customer education matters — high-CYA pools that use more chlorine are paying more for chemicals while getting less sanitation.