What is the purpose of a backflow preventer test cock?

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

Answer: (C)

The test cock on a backflow preventer is an access point used to verify the device’s operation. By attaching test equipment (like a gauge and hoses) to these ports, a technician can measure the pressures on the upstream and downstream sides and ensure the check valves and relief valve are working properly. This confirms the backflow preventer is truly preventing any reverse flow into the potable water supply.

It’s not used to regulate zone flow, drain the mainline for winterization, or measure soil moisture, which is why those other options don’t fit.