In reply to message posted by Bruce T:
Your standard Temperature and Pressure relief valve is set to discharge at 150 PSI water pressure and 210 degrees F. temperature.
(although they will pass water at less than these settings)
If you live in an area of high water pressure..(80 psi or higher..) your water regulator may have failed…
check your pressure with a guage.
If your water pressure is normal, then you could have a bad thermostat on your heater causing the temperature to get too high.
(this is more common in electric water heaters)
My first guess would be that your water pressure is too high.
gas water heaters thermostats dont fail very often but electric heaters thermostats do.
BUT electric heaters also have a built in safety device on the thermostat called a “HIGH LIMIT switch”
wich is supposed to shut down the heater in the event of extreme temperature.
turn off the gas or electic supply to your unit,
go to your local home improvement store and purchase an inexpensive water pressure guage that has 3/4″ hose threads and test you water pressure at the drain of your water heater.
If its 80 psi or or more than your pressure regulator has failed and needs to be rebuilt or replaced.
Also, do you know if the city water department has been doing any work in your area?
a pressure surge could cause this from them doing work in your area, but it is unlikely.
If your water pressure is lower than than 80 psi than your problem is with the heater thermostat(s)
call a plumber.
DO NOT ATTEMPT TO PLUG YOUR T&P VALVE!!!!!!
You can have an explosion!
Hi Bruce, some codes do state the following
” If city pressure exceeds 85 PSI to the fixtures then it must be reduced to 85 PSI or less and out side sill clcks can be full street pressure”
Local codes shal prevail of course.
My guess would be to replace the T&P as why take a chance on a $3.50 part Watts 3/4 Brass ASME rated valve