Free chlorine is the only number that matters

Free chlorine (FC) is the active sanitizer in your pool. Total chlorine (TC) is just FC plus the chlorine that’s already been used up fighting contaminants.

The math is simple: TC = FC + Combined Chlorine (CC). Combined chlorine, also called chloramines, is spent chlorine that bonded with sweat, sunscreen, pee, and whatever else blew into the water. It smells bad, irrit