What are the minimum and maximum allowed chlorine residual levels at the end of a line?

The minimum and maximum allowed chlorine residual levels at the end of a water distribution line are critical for ensuring safe drinking water quality and effective disinfection. A minimum level of 0.5 mg/L is necessary to provide sufficient disinfection, preventing the growth of harmful bacteria and pathogens. This level helps ensure that the water remains safe for consumption as it travels through the distribution system.

On the upper end, a maximum residual of 4 mg/L is established to prevent potential health risks. High levels of chlorine can result in unpleasant tastes, odors, and even adverse health effects in some sensitive populations. Staying within this range helps balance effective disinfection with consumer safety and comfort.

Each of the other options presents either a minimum level that is too low or maximum levels that are too high for the safe delivery of treated drinking water. By adhering to the range of 0.5 to 4 mg/L, water operators can adequately manage water quality throughout the distribution system.