Backflow Prevention Practice Exam

What condition may cause a pressure vacuum breaker to fail?

1. Excessive inlet pressure

2. Improper installation angle

3. Contaminated water supply

4. Failure to maintain a proper air gap

The correct answer is: Failure to maintain a proper air gap

A pressure vacuum breaker is designed to prevent backflow in irrigation and plumbing systems by maintaining a proper air gap. This air gap is essential for the device to function correctly, as it prevents back-siphonage, which can occur if there is a drop in pressure in the system. If the air gap is not properly maintained—either due to improper installation, clogging, or any other issues—there is a risk that water could flow backward into the potable water supply. Maintaining the air gap is crucial because, without it, there would be no barrier against potentially contaminated water from entering the clean water supply when negative pressure exists in the system. In essence, if the air gap is compromised, the pressure vacuum breaker cannot effectively prevent backflow, leading to possible contamination. Other factors, while they can impact the efficiency and functionality of the pressure vacuum breaker, do not directly relate to the critical air gap required to prevent backflow. Excessive inlet pressure may strain the device but does not necessarily directly cause it to fail in the same fundamental way as a compromised air gap does. Improper installation angle and a contaminated water supply can also be problematic, but they do not address the air gap issue that is essential for the pressure vacuum breaker’s operation.