The source of potable water used for disinfection and pressure testing shall be what prior to its use for new water mains?

• A. Groundwater
• B. Pre-flushing
• C. Treated wastewater
• D. Untreated river water

Answer: (B)

Pre-flushing the potable water before using it to fill and test a new main ensures the water entering the new pipeline is representative of the system and free from stagnation or debris. This step clears out any sediment, biofilm, or contaminants that could be present in storage or in the portion of the supply line that isn’t yet in use, and it helps establish a reliable disinfectant residual and water quality for the disinfection and pressure test. Using pre-flushed water supports effective disinfection, accurate test results, and safer, compliant operation of the new main.