Cross Connection Practice Exam

What happens to the relief valve of an appropriately installed Atmospheric Vacuum Breaker under backsiphonage conditions?

1. It closes tightly

2. It remains neutral

3. It falls in the open position

4. It leaks slightly

The correct answer is: It falls in the open position

When an Atmospheric Vacuum Breaker (AVB) is functioning under backsiphonage conditions, the relief valve plays a critical role in maintaining system integrity and preventing contamination. In these conditions, the pressure in the system drops, potentially allowing harmful substances to enter the potable water supply. The correct answer relates to the design and purpose of the AVB, particularly how it responds to negative pressure caused by backsiphonage. The relief valve is designed to open when there is a drop in pressure, thereby allowing air to enter the system. This action breaks the vacuum that could draw contaminants into the water supply. By falling into the open position, the relief valve effectively prevents backsiphonage, ensuring the water remains safe for consumption. This function is crucial in protecting public health and maintaining the safety of the water supply during pressure changes in the system.