What is the minimum free chlorine residual required in all parts of a distribution system?

The minimum free chlorine residual required in all parts of a distribution system is 0.5 mg/l. Maintaining this level is crucial for ensuring adequate disinfection throughout the water distribution system. Free chlorine serves as a strong disinfectant and helps to eliminate pathogens that may be present in the water, thereby protecting public health.

If the residual chlorine is too low, it may indicate insufficient disinfection, which could lead to waterborne diseases. Water treatment regulations, including those set by the Environmental Protection Agency (EPA), typically require this minimum residual to ensure that chlorine is actively present in the system to provide ongoing microbial protection as the water travels to consumers.

Higher residuals are often employed in specific scenarios to overcome challenges such as longer distribution systems or higher levels of contaminants, but 0.5 mg/l is the baseline requirement to ensure safe drinking water under standard conditions.