Cross Connection Practice Exam

During the second test of a Reduced Pressure Backflow Assembly, if the gauge drops from 8 psid to 7 psid when the bypass valve is opened, what is the probable cause?

1. Air in the system

2. Disc compression on check valve #2

3. Insufficient water pressure

4. Blocked bypass line

The correct answer is: Disc compression on check valve #2

When the gauge drops from 8 psid to 7 psid during the second test of a Reduced Pressure Backflow Assembly upon opening the bypass valve, it indicates a significant change in pressure that is likely related to the functioning of the backflow assembly. The correct choice highlights a potential issue with disc compression on check valve #2. The check valves in a Reduced Pressure backflow assembly work to prevent backflow, and if the disc on one of those valves is compressed or not seating properly, it can create a situation where the pressure differential is affected. When the bypass valve is opened, it allows for a change in flow patterns, and if check valve #2 is not adequately sealing due to compression, it can lead to a drop in pressure observed on the gauge. This drop indicates that water is not flowing as intended through the assembly, demonstrating the importance of properly functioning check valves to maintain the necessary pressure. In contrast, issues like air in the system could potentially cause pressure fluctuations, but would not specifically explain the drop seen when manipulating the bypass valve. Insufficient water pressure would suggest a systemic issue affecting all measured pressure, not a localized drop when bypassing one part of the assembly. A blocked bypass line would prevent flow through that path altogether,