Backflow Prevention Practice Exam

When should the air-inlet valve of a pressure vacuum breaker open?

1. When water starts flowing

2. When the pressure exceeds a certain limit

3. When there is a drop in system pressure

4. When shut-off valve 1 is opened

The correct answer is: When the pressure exceeds a certain limit

The air-inlet valve of a pressure vacuum breaker is designed to open when there is a drop in system pressure. This mechanism is essential for preventing backflow and protecting the potable water supply. When the system pressure decreases, it creates a vacuum within the line. The opening of the air-inlet valve allows air to enter the system, thereby equalizing the pressure and protecting against the siphon effect that could draw contaminated water back into the drinking supply. The air-inlet valve's operation is crucial because it ensures that if there is a loss of supply pressure, potentially hazardous backflow situations are mitigated by allowing air to enter the system rather than allowing potentially contaminated water to be sucked into the potable water line. This operation is an integral part of the backflow prevention strategy, ensuring safety and compliance with health standards. In contrast, the other choices do not accurately reflect the function of the air-inlet valve. The air-inlet valve does not open simply when water starts flowing or solely in response to pressure exceeding limits. It specifically functions in response to drops in system pressure to prevent backflow conditions. Additionally, the operation of valves in the system, such as a shut-off valve, does not directly correlate to the opening of the air-inlet valve