How long should a new water main be flushed and disinfected at 50 mg/L?

Flushing and disinfecting a new water main is crucial to ensure the system is free from contaminants and safe for public use. The recommended practice for disinfecting a new water main typically involves maintaining a chlorine concentration of 50 mg/L for a specific duration to effectively eliminate pathogens.

The correct duration for maintaining this chlorine level is generally 24 hours. This timeframe allows sufficient contact time for the chlorine to effectively disinfect the interior surfaces of the water main, ensuring that any harmful microorganisms are adequately killed. After this period, the system is usually flushed to remove residual chlorine and any disinfection by-products before going online.

While other durations exist for different applications or scenarios, in standard practices, 24 hours at 50 mg/L is recognized as the appropriate length of time for disinfection of new water mains. This protocol supports safe drinking water standards and is a critical step in water system management to guarantee public health.