What is the minimum free chlorine residual that should be maintained at distant points in the distribution system?

The minimum free chlorine residual that should be maintained at distant points in the distribution system is critical for ensuring water safety and quality. Maintaining a residual level of 0.2-0.5 mg/l and 1.0-2.0 mg/l is appropriate because it helps to effectively control microbial growth and protect the water supply throughout the distribution system. The lower range ensures that there is a baseline level of disinfectant available to manage potential contamination in areas where water may stagnate or where there are dead ends in the piping. The higher range is essential during peak demand or in sections of the system prone to higher risks of contamination.

Water systems must ensure that chlorine levels are sufficient to provide an adequate barrier against pathogens. Insufficient residual levels may lead to the regrowth of harmful microorganisms, compromising public health. Therefore, the correct range reflects a balance between efficacy in disinfection and safety for consumers, making it the recommended standard for maintaining free chlorine in water distribution systems.