Cross Connection Practice Exam

What is the likely reason for continuous discharge from the high side bleed valve of a PVB?

1. Fouled check valve

2. Leaking shutoff valve #1

3. Pressure changes in the system

4. Blocked relief valve

The correct answer is: Leaking shutoff valve #1

The continuous discharge from the high side bleed valve of a Pressure Vacuum Breaker (PVB) is most likely due to a leaking shutoff valve #1. The PVB is designed to allow air into the system during a backflow situation, and if the shutoff valve is leaking, it can cause the pressure in the system to drop, which would result in constant discharge from the bleed valve. A leaking shutoff valve prevents the proper sealing of the system, leading to an inability to maintain necessary pressure levels. This situation can create a scenario where the valve cannot properly perform its function, resulting in the continuous discharge observed at the bleed valve. In contrast, fouled check valves typically would lead to a different issue — namely the inability to prevent backflow or allow flow in the wrong direction, rather than a continuous discharge. Pressure changes in the system can cause variations in discharge but are not as direct a cause as a leaking valve itself. A blocked relief valve could lead to pressure buildup rather than continuous discharge, as it would prevent proper flow and venting when needed. Thus, the issue pinpointing a continuous discharge correlates most directly to a fault in the shutoff valve.