Water Heater Temperature Pressure Relief Valve (TPRV)

Technical Jargon is a topic used to provide more information on terms commonly seen in U.S. Inspect reports.

TPRV stands for Temperature Pressure Relief Valve. The TPRV is a valve on the water heater that will release water if excess pressure is built up within the appliance. Because the water released from the TPRV is very hot, it must be contained and discharged to a safe location by means of the pipe extension.

A TPRV can be found on all new water heaters. It is located either at the side or on top of the unit and can be recognized by the small operating lever. Just behind the lever is a flat metal ring on which is stamped the TPRV pressure and temperature ratings. Most valves are designed to discharge at 150F degrees and/or 210 pounds per square inch (psi). The TPR valves should be tested regularly to insure proper operation.

Because of the high pressure and temperature involved in a TPRV discharge, only certain materials can be used as a pipe extension. Standard PVC piping is not approved since it would not hold up to the temperature or pressure. CPVC has been tested and found capable of withstanding prolonged bursts from a water heater TPRV.

Smooth-walled copper, iron, and galvanized steel pipes are the materials recommended for pipe extensions. Corrugated piping can create turbulence within the pipe, which prevents pressure dispersion and increases the possibility of pipe rupture. Flexible piping is prone to crimping, which can have the same effect. Pipe extensions should be terminated within 6 inches of the floor, assuming that the water heater is located in an area where the floor will not be damaged by a discharge (e.g. the garage). If the water heater is located in an area where the floor could be damaged (e.g. the attic), the pipe extension should be extended to the exterior of the house, discharging within 6 inches of the ground.

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