Leaky T&P Valve?

Old 10-31-13, 12:05 PM
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Question Leaky T&P Valve?

Since I bought my house a little over 2 years ago, whenever I take a bath or a shower after I am done there is a puddle in my basement, coming from a straight pipe attached to what I now know is the T&P Valve on my water heater. I am not quite sure if it happens while the hot water is running or afterwards while it is refilling.

It is a gas tank that I believe is about 8-10 years old. There is also what I believe is an expansion tank hanging above it, but I am not sure. I can definitely get more information from both of the units when I get home from work tonight if that would be helpful.

I honestly hadn't though much of it until recently when I looked at the tag hanging from the valve and saw it was the T&P Valve, which concerned me that it might be getting over-pressure and could be dangerous. You'd think the extra water I am wasting on the concrete ground would have been enough, but I know little about water heaters so it wasn't high on my list.

Anyways, what could this be and what should I do to try and fix it? I haven't drained/cleaned the tank since I moved in, so I could do that if it might help. I have also thought of just replacing the valve to see if that helps, but wasn't sure if that was necessary or not.

Thank you in advance for any advice you can provide.
Old 10-31-13, 06:04 PM
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Are you on well or city water?

If you are on city water do you have a pressure reducing valve (PRV) to limit the city water pressure coming into the home?

First I would quickly pull the lever on the valve. This will open it causing a spurt of hot water which may clear any debris causing it to leak. If that does not stop the dripping then I would replace the valve. T&P valves do go bad and they are inexpensive and easy to replace so it's not a bad place to start.
Old 10-31-13, 06:24 PM
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#1 The water temp. needs to be no higher then 120 deg. check it.
There may be a air tank in the water line that looks something like this.
Watts Pre-Charged Non-Potable Water Expansion Tank-ET 15 at The Home Depot
There's what looks like a tire valve stem under a cap on the top of it, inside that tank there's a rubber bladder just like an inner tube. The air pressure in that bladder needs to be just below the incoming water pressure. If you push in the valve and water comes out instead of air the bladder is broken and the whole tank needs to be replaced.
If it's low on air you need to shut off the incoming water and relieve the water pressure by opening up faucets on the hot side before adding the air.
Sediment in the bottom of the tank has nothing to do with the PIV leaking but at least once a year you should be connecting up a garden hose to the drain valve on the bottom of the tank to drain out the solids in the bottom of the tank. No need to shut anything off, just open the drain and let it run a few min. If nothing comes out then the drain is plugged up and your going to have to use a metal coat hanger to stick in the shut off to break up the sediment.
Old 10-31-13, 10:12 PM
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I disagree with Joe concerning the 120 degree figure. That temperature is a dandy one for growing Legionella and other nasty things in the water. It also severely limits the amount of hot water available. That temperature was arrived at by concerns over some people being scalded by the water from the tap, something that can be avoided by installing a tempering valve immediately after the water heater outlet. Tempering valves mix a bit of cold water with the hot to produce a temperature in the 120 to 130 degree range for safety yet allow the tank itself to heat the water to the safer storage temperature of 140 degrees.

Joe is also mistaken about the air pressure in an expansion tank, it should be close to, or slightly above, the nominal water pressure. If it is below the nominal water pressure then you will lose a certain amount of the expansion capability of the tank. Setting the air pressure lower than the water pressure IS the correct procedure for a tank on a private well and pump system but not on a municipal water system. Further, his link is to heating system expansion tanks and not for expansion tanks used on potable (drinkable) water systems.

Finally, although his advice to annually (or more often depending on water quality) flushing the water heater tank is good there are very few, if any, factory drain valves on water heaters that have a straight-through passage that would allow the use of a wire to clear any sediment. Also, if you have a tank that has NOT been flushed for several years then flushing now MAY actually be the cause of failure.

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