Backflow Prevention Practice Exam

What is the force required to close a check valve in a dual check system?

1. 1 psid (6.9 kPa)

2. 2 psid (13.9 kPa)

3. 3 psid (20.7 kPa)

4. 4 psid (27.6 kPa)

The correct answer is: 1 psid (6.9 kPa)

In a dual check backflow prevention system, the check valves are designed to prevent the reverse flow of water, ensuring that the system operates effectively under normal conditions. The force required to close a check valve is specifically related to the pressure differential across the valve. The correct answer indicates that a pressure differential of 1 psid (pound per square inch differential) or 6.9 kPa is necessary to ensure that the check valve closes properly. This specific pressure is sufficient to overcome the pressure from the water flow trying to push the valve open, allowing the check valve to function effectively in preventing backflow. This understanding emphasizes the importance of maintaining appropriate pressure levels within a dual check system, as insufficient pressure might lead to valve failure and potential backflow issues, compromising water quality and safety. The other values presented signify higher pressure differentials that would be unnecessary for the typical functioning of a dual check system's valves.