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Leaking relief valve on new Bradford White electric water heater.

bob eck
bob eck Member Posts: 930
Plumbing contractor installed a new Bradford White residential 50 gallon electric water heater. The house has a well pump and well tank running 40-60 PSI. He also installed a thermal expansion tank on the cold water inlet to the water heater. He also has a Cash Acme water heater mixing valve on the new water heater. Water in tank is being stored at 140 to 150 degrees. The relief valve on the water heater is leaking very very slowly. What could be causing this problem.


  • Intplm.
    Intplm. Member Posts: 1,618
    edited April 2019
    Hello @bob eck.
    Double check your temperature readings. Make sure the upper and lower thermostats on the water heater are as you say they are. Check the mixing valve setting too. Should be around 120-130 deg. F.
    Also make sure the expansion tank has not lost its charge.
    Is there a backflow preventer installed on your water main? Some areas of the country require one even if you have a private well. If you have one installed, what type is it. They can cycle back and forth making the relief valve trickle.
    Lastly, the relief valve might have some debris under it not allowing it to seat properly. Pulling the trip lever up allowing water to flow from it could clear the debris away. (However,I would not do this unless you are prepared to change the relief valve!!) and you can get burned from scalding hot water. So if you haven't done this before , dont.

    All these things should be checked by the plumber who did the installation. Best thing to do is have them come back to look things over. The relief could just be defective.
  • hot_rod
    hot_rod Member Posts: 20,826
    temperature or pressure will cause a valve to relieve. If the installer held the T&P open while filling, some debris could be stuck in the seat if the valve
    usually a well tank supplies adequate thermal expansion, unless a check valve was added between the tank and supply to system?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 14,560
    @bob eck

    Check with the contractor. The new expansion tank may be charged to the wrong pressure not allowing for expansion. Take if off the system. You cant check the air pressure with water in the bladder. If your running 40-60psi around 55 psi of air should do it

    example: if you run 40-60 and have 80 psi of air in the tank its the same as having no expansion tank. If you run 40-60 and have 20psi of air in the tank same as having no expansion tank. pressures have to match within reason


    Bad relief valve..debris in seat
    too much water pressure
    electric heaters overshooting or running away....bad thermostat(s) or wired wrong