What is the minimum free chlorine residual required by health departments at distant points of the distribution system?

The minimum free chlorine residual required by health departments at distant points of the distribution system is typically set at 0.2 ppm. This standard is essential for ensuring that adequate disinfection is maintained throughout the water distribution system, particularly in areas that are far from the water treatment facility.

Maintaining a chlorine residual is critical for controlling microbial growth, preventing waterborne diseases, and ensuring the overall safety of drinking water. The level of 0.2 ppm signifies a balance between providing enough disinfectant to inhibit bacteria and maintaining palatability for consumers, as excessive chlorine can lead to unpleasant taste and odors.

In practice, if the residual is too low, it may indicate that the water has not been adequately disinfected, increasing the risk of contamination over long distances, particularly in systems with stagnant water. Hence, health departments enforce this minimum requirement to safeguard public health in the entire distribution network.