What is the free chlorine residual requirement for a distribution system?

The requirement for free chlorine residual in a distribution system is critical for ensuring the safety of drinking water. A free chlorine residual of 0.20 mg/L is the minimum standard accepted to effectively provide disinfection and protect against microbial contamination throughout the distribution system. This level helps maintain water quality from the point of treatment to the consumer's tap, ensuring that any pathogens potentially introduced during distribution are effectively controlled.

Having a free chlorine residual that meets this standard indicates that there is enough chemical agent present to inhibit bacterial growth and maintain a sanitary environment within the water system. Lower levels might not provide sufficient protection, while higher levels could lead to issues such as taste and odor complaints. Therefore, maintaining a free chlorine level of 0.20 mg/L balances the need for safety and water quality.