Water heater question: T&P valve.

[mission16]

Situation:
-Rheem 50 electric, 9 yr
-less than 90 days old
-t&p valve engaged.
-turned power off.
-installed new valve next day.
-within a minute of turning water back on, NEW valve engages
-power is still off, so no heat.
- no other leaks in the house.

Discuss.

[blackhat]

Its a temperature and pressure relief. 125 psi or 220 degrees. You are exceeding one or the other. Do you have a small thermal expansion tank on your system? It may have failed. A check valve and no expansion tank? A pressure reg on the incoming water line? A sticking pressure switch on a pump?

[A Squared]

mission16 said:

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.......-t&p valve engaged. ........within a minute of turning water back on, NEW valve engages........

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When you say "engage", do you mean "opens and releases water" ?

If so, I'd ask the same questions as Blackhat (he's a pretty clever dude on plumbing and heating stuff)

My guess is that it's pressure causing the valve to open. Get a test pressure gauge like this.

Costs about 10 bucks and has a hose fitting so you can screw it onto the drain outlet of your heater, or anywhere you have a hose bibb. Find out what your normal system pressure by attaching the gauge with the heater off. Water pressure can vary during the day depending on neighborhood system demands, or pump cycles on a private system. The gauge has a "telltale" needle which stays at the highest reading, so you can leave it for a day and see what the highest pressure was. If your system supply pressure isn't causing the T & P valve to open, then test the pressure of your hot water. This can be different if there is a check valve on your supply, or you have a private system. Anyway, when the heater heats the water it expands and if it has no place to go, the pressure will rise. If the gauge shows that the pressure is rising wen the heater is heating, then you have a closed system with no/not enough expansion space. You may need to install an expansion tank on your hot water system. If you already have an expansion tank on your hot water system, check to see if it has failed. The rubber diaphragm inside can fail, or the air precharge can leak out.

[mission16]

engages=water.

put a pressure gauge on an outside spigot and it pinned the needle, 200psi+
Clearly a regulator, right?

So how much pressure IS in the water main out on the street?

[blackhat]

That's nuts. It'll tear faucets apart. Get the regulater fixed now.

[A Squared]

mission16 said:

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engages=water.

put a pressure gauge on an outside spigot and it pinned the needle, 200psi+
Clearly a regulator, right?

So how much pressure IS in the water main out on the street?

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I think you've found your problem. Dos your shower peel your skin off when you get in? Yeah, seems like it's a failed regulation.

[joe1086]

Assuming city water, isn't even 100 psi in the high range? Ours comes in around 80 and we dial it back to 50.

[Splinter Puller]

Mine was coming into the house at around 80psi. I had a main valve fail a month ago and when they were here to fix it they noticed the pressure and installed a reducer to get it down to 50psi.