Which statement best describes why a backflow preventer test cock is used?

• A. To drain the mainline for winterization.
• B. To regulate water pressure in the mainline.
• C. To attach test equipment and verify the backflow preventer is functioning correctly.
• D. To measure soil moisture.

Answer: (C)

A backflow preventer test cock provides access points for testing equipment so you can verify the device is working correctly. When testing, a certified backflow test kit with hoses and gauges is connected to these ports. By opening the individual test cocks, you can measure the pressures on the upstream and downstream sides of each valve and the relief port, confirming that the check valves seat properly and that the device prevents backflow as intended. This is how the unit’s functionality is confirmed to meet code. The ports aren’t for draining the mainline, regulating pressure, or measuring soil moisture; their purpose is specifically to enable testing and verification of the backflow preventer.