Backflow Prevention Practice Exam

What does continuous flow from a pressure vacuum breaker's test cock 2 indicate when shut-off valve 1 is closed?

1. Backsiphonage backflow

2. A leaking check valve

3. A failed air-inlet valve

4. Backpressure backflow

The correct answer is: Backpressure backflow

When observing continuous flow from a pressure vacuum breaker’s test cock when the shut-off valve is closed, it suggests that there is a condition allowing water to flow against the intended flow direction. This scenario specifically indicates a failure related to the pressure regulation and air intake function of the device. In this context, backpressure backflow occurs when there is an increase in pressure downstream in a system, potentially forcing water back into the supply line. The pressure vacuum breaker is designed to prevent such backflow scenarios by maintaining air intake and thereby relieving pressure. If the air-inlet valve fails to open when it should, it can't equalize pressure, leading to backpressure conditions that allow continuous flow despite the shut-off valve being closed. The other options suggest different failure mechanisms or conditions, such as backsiphonage or leakage, which do not align with the observed situation of continuous water flow under these specific circumstances. Hence, identifying the flow as backpressure backflow reveals an understanding of the operational failures within the system and emphasizes the importance of regular maintenance and monitoring of backflow prevention assemblies to ensure they function as intended.