The relief valve of an RPZ must open at what pressure?

The relief valve of a Reduced Pressure Zone (RPZ) backflow preventer is designed to open at a specified pressure differential to ensure the system maintains safety and proper functioning. The correct pressure at which the relief valve must open is 2.0 psi, which is meant to provide an acceptable level of protection against backflow conditions.

When the pressure in the downstream system drops below a certain threshold, the relief valve activates to discharge the potentially contaminated water from the system, preventing backflow into the potable water supply. The setting of 2.0 psi is critical, as it ensures that there's sufficient pressure differential to prevent contaminants from entering the clean water supply while also ensuring that the system remains operational under normal conditions.

This specific pressure setting helps in maintaining the desired safe operation of the RPZ and is a recognized standard in backflow prevention practices, ensuring compliance with plumbing codes and safety standards.