During basic disinfection after a water main break, how is flushing completed?

• A. Flush until the water runs clear
• B. Flush until discolored water is gone
• C. Use a fixed 60-minute flush
• D. Do not flush

Answer: (B)

Flushing after basic disinfection aims to push out the disturbed sediments and any metal compounds released during the break so the water entering the distribution system is visually clean and meets quality standards. The best way to know you’ve cleared the system is to flush until discoloration is gone. Discolored water signals suspended solids, iron, or manganese that can affect both aesthetics and safety; removing that discoloration indicates those materials have been cleared from the line and the water is returning to normal quality. A fixed time or doing nothing isn’t reliable, because the amount of disturbed material varies with each break and repair, and discoloration provides a practical cue that the system has been sufficiently flushed. After discoloration disappears, operate the system as usual and perform the necessary residual disinfectant and water-quality testing.