What does constant discharge from the relief valve of a reduced pressure principle assembly usually indicate?

Constant discharge from the relief valve of a reduced pressure principle assembly typically indicates that there is an issue with the check valves, specifically a leaking first check valve. In the context of a reduced pressure zone (RPZ), the check valves are critical for maintaining the necessary pressure differential to prevent backflow. If the first check valve is leaking, it will allow water to flow back into the area that the RPZ is meant to protect, causing the relief valve to activate and continuously discharge in an effort to relieve the excessive pressure buildup caused by this backflow.

This behavior is specifically designed to prevent any potential contamination of the potable water supply. The relief valve acts as a safeguard, ensuring that any increase in pressure due to backflow is released to prevent hazardous substances from entering the drinking water system.

While other options may present potential issues within a backflow prevention assembly, the scenario of continuous discharge from the relief valve most directly correlates with a failure in the first check valve, thus indicating its leaking condition.