After connecting overhead piping, the underground main may be flushed.

• A. Never
• B. Only after a test
• C. False
• D. True

Answer: (D)

Flushing is a commissioning step used to clear debris and air from a piping system. When overhead piping is connected to an underground main, debris from cutting, threading, or backfilling can be carried into the underground line. Flushing pushes water through the main to remove those sediments and to purge air, ensuring the line is clean and ready for testing or service. That’s why the statement is true: it may be flushed as part of proper installation and preparation, following the project specs and codes with the appropriate valves and drainage in place.