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malahide66 07-05-2009 12:44 PM

hot water heater??????????????
I have an 80 gallon hot water heater that is dripping from the pressure relief valve.not much, not even a pint in a few days, I was told to shut the power off (its electric) shut off the feed drain some water from the tank and then try releasing the pressure.
well i shut off the water hooked up a hose to the drain and no water came out i then tried the pressure relief valve and got nothing. am i doing something wrong is it just junk and need to call a plumber? any advice would be appreciated.

Houndawg 07-05-2009 01:36 PM

The bottom of the tank is probably filled with solids from the minerals in the water. These solids will block the flow of water and plug the valve.
Usually when this happens, the water heater is very old, and the water is very hard. You can remove the drain valve to try to clear out the deposits, but before tackling such an operation, be prepared to replace the heater, as drain valve removal has been known to spin out the valve tapping due to corrosion. When this happens, it's new heater time.

The "relief valve" is actually a Temperature-Pressure relief valve. When the water is heated the expansion due to heating causes an increase in pressure in the vessel. When the pressure builds to the set point (Usually 125 psi) the relief valve relieves the pressure in the tank.
You need to establish an air cushion to correct this situation.
I found the best way is to install a "Bladder tank" at the cold water inlet. This simple device compensates for water expansion and contraction during the heat cycle.
The temp/pressure (TP Valve) is not designed to cycle too many times. After repeated cycling the seat will become damaged and the valve will leak all the time.

malahide66 07-05-2009 01:41 PM

thanks we were thinking of just replacing it anyway.

PaliBob 07-05-2009 04:29 PM

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.......the seat will become damaged and the valve will leak all the time.
Congratulations to Houndawg for an excellent first post.

malahide66 I had a similar problem with the TPR on my Water Tank so I replaced it with a new $12 TPR . It will not make an old tank like new but it should fix the dripping. The TPR design is pretty much standardized

kenmac 07-05-2009 06:21 PM

You will need to test water pressure to know for sure. But you may require an expansion tank/ water pressure regulator on the main water line

PaliBob 07-05-2009 07:34 PM

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Originally Posted by kenmac (Post 297528)
You will need to test water pressure to know for sure.

DIY'ers That are tool geeks have one of these:


kenmac 07-05-2009 09:21 PM


Originally Posted by PaliBob (Post 297558)
DIY'ers That are tool geeks have one of these:

I agree,:yes:,, Being in the plumbing bus. I've been using them for years

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