Water heater pressure valve leaking

The pressure valve on my hot water heater just started dripping the other day...........it leaks maybe a cup of water every couple of days.
What gives? Do I need to replace it? I opened it and let it reseat but no help.

King3244

Either it's faulty - in which case you should just replace the Temp/Pressure valve - or your heater is building up too much heat and/or pressure.

Is the heater set to a very high temperature or have you noticed the water being much hotter than it used to be?

I'd replace the pressure/temp valve and if the new one drips then it is an indication that there is indeed an issue causing excessive heat/pressure that you should get resolved (i.e. service call or new tank).

Do you have a pressure-reducing valve on your main water line? If so, you may have a "closed system" since many PRVs have a one-way check valve. When water in the heater heats up, it expands, and if there's a check valve at a PRV or the water meter, pressure may build up in the system to temporarily "pop" the temperature/pressure valve at the heater.

The solution for that problem is a water expansion tank.

Yes I do have a pressure reducing valve from the main line into the house. That may very well be the problem. I will monitor it for awhile and see what happens. The tank is the original one for the house which makes it about 14 years old.........so it is getting to the end of its life cycle anyway.
Thanks for the input guys.

When you refer to the 14-year-old tank, do you mean you have a separate water heater expansion tank? Or are you refering to the water heater itself?

If you do have a separate expansion tank, you can check the air pressure in it with a tire gauge. Should be set at the same pressure as your home's water pressure. I had a boiler valve put inline with my expansion tank, just so I can attach a water pressure gauge and keep an eye on what my home's water pressure is running.

No expanion tank.

No expansion tank on a system with a pressure reducing valve may be the problem.