What is the accepted minimum level of free chlorine required to destroy harmful organisms in pool water?

The accepted minimum level of free chlorine required to effectively destroy harmful organisms in pool water is 3 parts per million (ppm). This concentration is recognized as a standard to maintain adequate sanitation levels. Free chlorine acts as a disinfectant, targeting bacteria, viruses, and other pathogens that can compromise swimmer health. At this level, chlorine is able to provide effective oxidation and disinfection, ensuring the water remains safe for recreational use.

While lower levels may be suitable for general maintenance or aesthetic purposes, they might not be sufficient to ensure complete disinfection, especially in pools with high bather loads or during periods of heavy use. Higher levels, such as 5 ppm or 10 ppm, can indeed offer greater protection, but they may also lead to irritation of skin and eyes for swimmers and can result in chlorine odors that can discourage usage. Thus, the 3 ppm threshold is considered a balanced approach to maintaining water safety in a pool environment.