When should free chlorine be measured?
Free Chlorine applications
Free chlorine is typically measured in drinking water disinfection systems using chlorine gas or sodium hypochlorite, to find whether the water system contains enough disinfectant. Typical levels of free chlorine in drinking water are 0.2 - 2.0 mg/L Cl2, though levels can be as high as 5.0 mg/L. If the chlorine levels will be reported to a regulatory agency, it would be recommended to confirm with local regulations which form of chlorine (free or total) to measure and which methodology to utilize.