Cross Connection Practice Exam

What effect does opening the high side and then the low side control valves have on a properly functioning Reduced Pressure Principle Assembly?

1. The differential will increase

2. The differential will decrease

3. No effect on differential

4. It will cause a backflow

The correct answer is: The differential will decrease

Opening the high side control valve and then the low side control valve of a Reduced Pressure Principle Assembly (RPPA) will result in a decrease in the differential pressure across the assembly. This is because the RPPA is designed to maintain a specific pressure differential between the inlet and the outlet to ensure that contaminants do not flow back into the potable water supply. When the high side valve is opened, the flow of water increases, which can temporarily elevate the pressure on the inlet side. However, simultaneously opening the low side control valve allows for more water to exit the assembly, which reduces the pressure downstream. The combination of these two actions effectively decreases the pressure differential, as water flow through the assembly increases without a corresponding increase in pressure in the zone being supplied. Maintaining the correct differential pressure is crucial for the RPPA to function effectively as a backflow prevention device. If the differential were to increase or remain unchanged, it could indicate potential malfunction or inadequate protection against backflow, which the RPPA is specifically designed to prevent. Therefore, the action of opening both valves results in a decrease in differential pressure, confirming the correct choice.