Backflow Prevention Practice Exam

When both shut-off valves are closed on a reduced pressure principle assembly and test cock 2 is opened, what result should the tester expect?

1. Check valve number 1 to open

2. Continuous flow from the test cock

3. No flow from the test cock

4. Relief valve discharge

The correct answer is: Relief valve discharge

When both shut-off valves on a reduced pressure principle assembly are closed and test cock 2 is opened, the tester should expect the relief valve to discharge. This occurs because the reduced pressure zone created by the assembly serves as a backflow prevention mechanism. In normal operation, when there is no flow (as in the scenario described), pressure can drop in the zone, which can trigger the relief valve to open. The relief valve is designed to maintain a specific pressure and ensure that if the pressure within the assembly drops below a certain point, the valve will discharge to prevent a backflow situation, thus protecting the potable water supply. This is a crucial feature of a reduced pressure zone assembly as it prevents contamination of the water supply from backflow conditions. In contrast, if the test cock were to be opened under normal conditions without the shut-off valves being closed, you might observe other outcomes, such as flow from the test cock, depending on the system’s pressure dynamics. However, since both shut-off valves are closed, it creates a condition where the only allowable action is for the relief valve to discharge, hence focusing on why the correct answer is D.