Which component is measured during a directional flow test on an RPZ assembly?

During a directional flow test on a Reduced Pressure Zone (RPZ) assembly, the focus is on evaluating the performance and sealing capability of the device's internal components. The specific component measured during this test is Check Valve Number Two.

This check valve is critical because it serves to prevent backflow from the downstream side of the RPZ back into the system. The directional flow test ensures that the valve operates properly and can maintain the necessary seal to protect the potable water supply. If Check Valve Number Two does not function correctly, it may allow contaminated water to flow back into the drinking water supply, which poses significant health risks.

The design of the RPZ assembly relies on both check valves to work in conjunction, but Check Valve Number Two is specifically tested for its ability to prevent reverse flow under backpressure conditions. The relief valve, while important, operates under different circumstances and is not the primary focus of the directional flow test. Similarly, Test Cock Number Four is a connection point used for taking measurements but is not a component that is directly tested for function in this particular scenario.