What causes a relief valve to open up early? “5.0 PSID or above”

Technically when a relief valves opening point is above 5.0 PSID it is considered a failure and the relief valve should be repaired.

The relief valve is a resilient soft seated design. In the example photo above, the relief valve disc is mounted in the relief valve assembly so it is flush to the hard plastic outer ring. This hard plastic outer ring is designed to seat on the outer flat edge of the relief valve seat, there by the raised inside sharp edge of the seat only penetrates into the soft resilient disc material specified by engineering specifications. “If the relief valve on the assembly you’re testing opens up early it is because the relief valve is not seating 100% per specifications on the relief valve seat.”

For example if the relief valve seat is supposed to penetrate the relief valve disc by 30% but the relief valve seat is only partially penetrating the disc by 5%, the movement the relief valve must move before the relief valve begins to vent water is reduced by 25%, i.e. the relief valve opening early or at an excessively high PSID.

In short, regardless of the design; if your relief valve is opening above 5.0 PSID then it is safe to assume that your relief valve is not seating 100% and therefore is not working properly. To avoid property damage and a possible emergency repair this should be addressed at the time of service.