Temperature/pressure relief valve

Plumbing · Conventional Tank Type Water Heaters · printed page 279 (PDF page 280)

Original page Sign in to save

Book index entries

Temperature/Pressure Relief Valve – Water Heater Temperature/Pressure Relief Valve Plumbing

Text in the illustration

not more than 6”
pressure:
OK
temperature:
spring
poppet
valve
sensor
probe
to
drain
>150 PSI
manual relief lever can also be
used to open poppet valve
water pressure
overcomes spring
pressure and opens
poppet valve
>210°F
piston
wax fill
heat expands wax fill
in probe - pushing
piston and opening
note:
mechanism
simplified
for clarity
hot
cold
<6”
not more
than 6”
electric
water heater

Generated explanation

The illustration shows a temperature/pressure relief valve installed near the top of an electric tank-type water heater, with a discharge pipe extending down to within 6 inches of the floor. Three simplified valve cross-sections show normal operation, relief under pressure exceeding 150 PSI, and relief under temperature exceeding 210°F. Under excess pressure, water overcomes the spring force and opens the poppet valve to the drain outlet. Under excess temperature, expanding wax in the sensor probe pushes a piston to open the valve; a manual relief lever can also open the poppet. The tank drawing shows hot and cold connections and a less-than-6-inch dimension locating the relief valve near the tank top.