Re: Causes of Failure of Pressure Relief Valve
Posted by Deb on July 14, 2004 at 22:47:56:
In response to Re: Causes of Failure of Pressure Relief Valve
: Recently our town replaced the water meters with new ones, and at the same time they installed check valves on the supply line to the residences. Within two weeks, my pressure relief valve failed. I don't believe it was merely a coincidence.

: My question is, what are the causes of failure of pressure relief valves? Would the absence of an expansion tank in the residence system, coupled with a complete cool down and subsequent reheat of the residence hot water tank, cause such a failure (high pressure, leaks in valve itself, etc.)?

You are speaking of a P & T failure, when I am suspecting that it did exactly what it was supposed to. The check valves created a closed system. And (exactly as you suspect) thermal expansion is causing excess pressure, which in turn is causing the T & P valves to open. An expansion tank should generally be installed on any closed system.
The Pipewench

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