Which scenario would necessitate the opening of the relief valve in an RP assembly?

In a Reduced Pressure (RP) assembly, the relief valve is a critical component designed to protect the potable water supply from contamination due to backflow, particularly under fluctuating pressure conditions. The relief valve opens when there is a drop in supply pressure that results in the pressure within the assembly falling below the pressure in the downstream piping.

When this happens, the system is at risk of backflow, which can allow non-potable fluids to enter the potable water system. By opening the relief valve, the RP assembly releases the lower-pressure water, thereby preventing the backflow scenario from contaminating the supply. This safety feature helps maintain the integrity of the water supply and prevents any potential health risks associated with backflow.

Other scenarios, such as normal operational conditions, increased supply pressure, or a general decrease in supply pressure that does not create a condition for backflow, do not require the relief valve to open. The operation of the relief valve is specifically tied to conditions that might lead to negative pressure situations and the risk of backflow.