water heater pressure relief valve

[ssardone]

on my '01 320 I've noticed that my water heater pressure relief valve leaks when the heater reaches full temperature. It doesn't leak when heated by the engine or when water pressure is on but the heater turned off. It is a seaward 6 gallon. Does the heater have an adjustable thermostat? It seems like replacing the PRV, heating coil and or thermostat is not that expensive but only want to replace what is necessary.

thanks for the help

Steve

 

[Alan]

The PRV is rarely put into action. They fail simply from lack of use. They are inexpensive and easy to replace. Use teflon tape on the threads before you install.

 

[ssardone]

thanks-I'll get one ordered.

steve

 

[Don12364]

Perhaps it always did!

A 6 US gallon steel tank heated from 20°C (68°F) to 60°C (140°F) increases its volume by 33ml (1.1 US oz).
6 US Gallons of water increases in volume by approx 414ml (14 US oz).
The difference being 381ml (12.9 US oz or 0.8 US pint).
The system is sealed.
Where else can it all go?
Perhaps, like people, the arteries (pipes) harden after a few years?

If you haven't already got one, an hydraulic accumulator, as well as improving the water flow by stopping the pump from cycling, should also cure this leakage.

 

[ssardone]

Re: Perhaps it always did!

I understand what you are saying about expansion and will install an accumulator next year. But, the valve never stops leaking which I think it would after the expansion pressure was leaked out......

Steve

 

[Alan]

All of this is very true, but the PRV is designed specifically to contain the rise in pressure. It is only called into action when the pressure rises to a predetermined unsafe level. Only then will it open to relieve some of this pressure. Most systems never reach this threshold and therefore the valve never opens.

 

[Dan Johnson]

PRV...

You should be able to obtain a direct replacement at any home center store (HomeyD, Lowes, Ace or Tru-Value, etc.) without having to order one and pay high cost and shipping.

 

[CaptDanS]

Re: PRV...

Do not buy a replacement at a home store. The valves sold for home use open at 150 psi. The ones designed for marine use open at 75psi. Since most pressure water systems have no other relief valves in the system, you may damage other components if you have a pressure spike.
Dan Sheehan

 

[ssardone]

well thanks for all the help. I ordered a prv and a thermostat from torresons for 30 bucks and after the install it appears to have fixed the problem. I put a new thermostat in even though I didn't know if it needed it-it was only 10 bucks. Hot water with no leaks.

Steve