Before attaching a test kit to a Reduced Pressure Zone (RPZ), why does the tester open test cock 4 and allow it to trickle?

Opening test cock 4 and allowing it to trickle before attaching a test kit to a Reduced Pressure Zone (RPZ) serves an important purpose related to the operation of the relief valve. When the tester opens this cock, it helps to ensure that there is no sudden pressure buildup that could cause the relief valve to prematurely open.

In an RPZ assembly, the relief valve is designed to open and discharge water if the pressure in the zone drops below a certain threshold, which is intended to prevent backflow conditions. By trickling water from test cock 4, the tester can maintain a controlled flow that allows the testing apparatus to be connected smoothly and ensures that the internal pressures stabilize.

This action helps to avoid any unintended activation of the relief valve that might occur if there is a sudden change in water pressure. It contributes to accurate pressure readings during the testing process, ensuring valid test results and system integrity.