A plumber is replacing a reduced-pressure principle (RP) backflow preventer. After installation, the device needs to be tested. Which of the following conditions, if observed during testing, would indicate a failure of the device?

Question: A plumber is replacing a reduced-pressure principle (RP) backflow preventer. After installation, the device needs to be tested. Which of the following conditions, if observed during testing, would indicate a failure of the device?

Answer options:

• Both check valves hold tightly under backpressure.
• The differential pressure relief valve opens to discharge water.
• The pressure in the zone between the check valves is less than the supply pressure. ✅ The relief valve continually discharges water even when there is no backpressure.

Correct answer: The relief valve continually discharges water even when there is no backpressure.

Explanation: If the relief valve continually discharges water even without backpressure, it indicates a malfunction, likely due to a fouled or damaged check valve, preventing proper sealing and maintaining the reduced pressure zone. The relief valve should only discharge under specific differential pressure conditions, not continuously.