Backflow Prevention Practice Exam

Which device is utilized as a last line of defense against backflow in irrigation systems?

1. Double check valve

2. Reduced pressure valve

3. Spill-resistant vacuum breaker

4. Air gap

The correct answer is: Reduced pressure valve

The reduced pressure valve is specifically designed to protect against backflow in situations where the potential for contamination exists, making it an effective last line of defense in irrigation systems. This device functions by maintaining a pressure differential and utilizing two independently acting check valves with a pressure relief valve located between them. The operation of the reduced pressure valve ensures that any backflow that may occur is diverted away from the potable water supply, preventing contaminants from entering the drinking water system. It is particularly advantageous in scenarios where there might be severe cross-connections, which increase the risk of backflow from irrigation to the potable water supply. In comparison, other devices like the double check valve, spill-resistant vacuum breaker, and air gap serve specific purposes in backflow prevention but may not provide the same level of protection under high hazard conditions. For instance, double check valves are effective for low to moderate contamination risks but do not protect as effectively against backsiphonage, and vacuum breakers are limited to protecting against backpressure. An air gap, while a very effective method for backflow prevention, may not fit all irrigation configurations due to space and installation constraints.