Which test is used to move a master pressure regulating device from its seat?

• A. Drain test
• B. Pressure test
• C. Main drain
• D. Flow test

Answer: (C)

The main drain test is used to move a master pressure regulating device from its seat. The master regulator sits tight against its seat under normal system pressure, and to verify it can open and relieve pressure when needed, you intentionally drain the system through the main drain. Opening that path lowers the pressure enough for the regulator to move off its seat and vent water, confirming it will respond correctly during actual operation. This specific test is about verifying the regulator’s ability to actuate, which is why it’s used for this purpose.

Other tests don’t target this movement: a drain test checks the function of individual drainage points and leaks, a pressure test focuses on leaks under elevated pressure without exercising the regulator’s seating, and a flow test measures discharge capacity rather than the regulator’s seating/relief action.