Backflow Prevention Practice Exam

Which condition signifies backpressure backflow?

1. Water flowing from test cock 1

2. Dry conditions at the air-inlet

3. Pressure fluctuations during flow

4. Flow continues with shut-off valve 2 open

The correct answer is: Flow continues with shut-off valve 2 open

The condition that signifies backpressure backflow is the situation where flow continues even with a shut-off valve open. This indicates that the pressure upstream of the valve exceeds the pressure downstream, allowing water to flow in the opposite direction. In a normal scenario, shutting off a valve would cease all flow; however, if backpressure exists, it overcomes the resistance of the shut-off valve, allowing the water to flow despite it being in an open state. Backpressure backflow often occurs in systems where water is being forced back into the supply, typically due to an elevation difference or a booster pump that creates higher pressure in the system. In contrast, the other conditions mentioned do not directly indicate backpressure backflow. For instance, water flowing from a test cock might suggest normal operational testing rather than backflow conditions. Dry conditions at the air-inlet would indicate that there’s no siphoning action occurring, and pressure fluctuations during flow may relate to other hydraulic factors but do not necessarily confirm backpressure backflow. Hence, the situation where flow continues with a shut-off valve open is a clear indicator of backpressure backflow.