A partial flow test of a master pressure reducing valve may be performed using which method?

• A. Closing the main shut off valves.
• B. Main drain test on a quarterly basis.
• C. Opening the inspectors test valve annually.
• D. Turning the fire pump on and opening the case relief valve

Answer: (B)

Testing a master pressure-reducing valve with partial flow relies on creating a small, controlled discharge path so you can observe the valve’s response without draining or pressurizing the entire system. Using the main drain to perform this test provides a predictable, limited flow that lets you verify that the PRV is reducing the upstream pressure to the proper downstream level and that the discharge path and valve operate correctly. Routine main drain testing on a quarterly basis ensures this pathway and the valve performance stay reliable over time.

Other methods would not give you that controlled partial flow. Closing the main shut-off valves would shut off service entirely, not test the valve’s normal operating response. Opening the inspector’s test valve changes the test setup to a bypass scenario that's not the standard partial-flow condition. Turning the fire pump on and opening the case relief valve creates high-flow, pump-driven conditions that are not representative of a partial-flow test and could introduce unnecessary risk.