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Over The Network

Water heater relief valve

by Tom Jones

My water heater developed a problem which manifested itself in water being periodically ejected from the pressure/temperature relief valve. If left alone, the fresh water tank would eventually be emptied. Several folks offered various suggestions, including:

  • Replacing the possibly lost head of air in the hot water tank.
  • Manually operating the relief valve to expel any debris trapped in the seal.
  • Replacing the relief valve.
  • Flushing any debris from the tank via the drain.


    • The tank had clearly lost the head of air and this was my first fix. The procedure for doing this is:

      • Turn off the water pump, open the drain valve and drain the tank (be sure the water has cooled before attempting this).
      • Close the drain valve.
      • Open a hot water faucet.
      • Re-fill the hot water tank, either from city water or, as in my case, by turning the water pump back on.
      • Turn off the hot water faucet when the tank has filled.


        • Next I manually operated the relief valve. But, re-heating the water resulted in the relief valve ejecting a continuous stream of water.

          Time to buy a new relief valve. A trip to an RV parts store produced two reliefe valves, one with 1" threads and one, twice the price, with 0.5" threads like mine. However, both of these valves were marked 210 degrees and 150 psi, whereas the one I removed was marked 210 degrees and 75 psi. Off to another store who didn't have it in stock, but ordered one for overnight delivery. I stressed the 75 psi rating.

          The following day I picked up the new valve and found that, although it had the same part number, it was marked 150 psi. I then called Tech Support at Atwood, the manufacturer of the tank. They politely explained that the 75 psi valve was a requirement for Europe, although the tank itself was rated at 350 psi and the 150 psi valve would be just fine.

          Suggestions incorporated in the above were offered by Karl Kolbus, Don Jordan and Ron Ruward.