Water heater TP valve leaking

[CEPenworks]

I have a 3 year old tank water heater and the TP valve started to leak. I put a bucket under the tube coming out of the valve and after a week or so I would collect maybe a gallon of water. I switched out the valve and the new one does the same thing. I do not have the temp turned up high. Any idea what could be the problem?

[Roly]

I have a 3 year old tank water heater and the TP valve started to leak. I put a bucket under the tube coming out of the valve and after a week or so I would collect maybe a gallon of water. I switched out the valve and the new one does the same thing. I do not have the temp turned up high. Any idea what could be the problem?

Did they change out the water meter lately?  If so, new ones have a back flow preventer in them.   When the water heater heats the water it expands and now has no where to go which builds the pressure up.  If this is the case, you will need an expansion tank.   You can verify this with a pressure meter with a push needle that indicates the max pressure, not expensive.  Mostly happens in winter when the water has most temperature change.   Expansion tanks are required in my area with tank install.   Roly

[jteneyck]

Did they change out the water meter lately?  If so, new ones have a back flow preventer in them.   When the water heater heats the water it expands and now has no where to go which builds the pressure up.  If this is the case, you will need an expansion tank.   You can verify this with a pressure meter with a push needle that indicates the max pressure, not expensive.  Mostly happens in winter when the water has most temperature change.   Expansion tanks are required in my area with tank install.   Roly

This happened to me when the town installed new water meters.  It had a back flow preventer with it.  The town failed to tell people and several people had their basement flood when the T/P opened and then failed to close.  Fortunately, that didn't happen to me.  Several months later I got a letter from the town saying there might be a problem and to install an expansion tank, which I had done the day after I had the problem. 

John

[CEPenworks]

The water meter was changed several years ago after it exploded. The leak started a couple months ago so I don't think it is associated with the meter.

[Roly]

The water meter was changed several years ago after it exploded. The leak started a couple months ago so I don't think it is associated with the meter.

Hook up a pressure gauge and leave it overnight, then check max pressure.     It could also be a pressure regulator, or the water system pressure increased. 
Something like this Watts 3/4 in. Plastic Water Pressure Test Gauge DP IWTG - The Home Depot    Needs a push hand like this one to record max pressure.   Roly

[blackhat]

It’s a temperature and pressure relief valve. If the temp side actuated, it takes 5 to 10 gallons minimum to drop the water temp and reseat the valve. That’s not what you’re seeing. Pressure actuation, especially a gradual build up can be relieved with ounces of water dumped. Sound familiar?  

Install a small expansion tank, designed for potable water, in either hot or cold line close to the heater.

[CEPenworks]

The pressure gauge seems an inexpensive test. If it is a pressure thing then I still wonder what changed several months ago. I may never know.

[Roly]

The pressure gauge seems an inexpensive test. If it is a pressure thing then I still wonder what changed several months ago. I may never know.

Remember the incoming water is much colder than it was several months ago and is expanding more when heated.   Roly

[jteneyck]

The pressure gauge seems an inexpensive test. If it is a pressure thing then I still wonder what changed several months ago. I may never know.

Did you recently repair a leaky faucet?  

John

[Snipe Hunter]

After trying lots of different things dealing with plumbing and HVAC, I now just ask Blackhat's advice and follow it. Live is so much simpler that way.