Leaking TPR Valve

[Chip O'Brian]

Had a plumber tell me that dripping is normal at discharge pipe for TPR valve. Any thoughts, opions. I have done a couple inspections this is a first.

[John Arnold]

Wrong. It's leaking for a reason. Either the pressure in the tank is too high, or the valve is defective, or the valve won't seat properly due to corrosion or whatever. Needs fixin', dang it.

[Rick Hurst]

He's probably the one who replaced it, so he's feeding you a line.

It could possibly lead to wood decay on that wood siding which should not be below the pavers.

[Scott Patterson]

Had a plumber tell me that dripping is normal at discharge pipe for TPR valve. Any thoughts, opions. I have done a couple inspections this is a first.

As others have said, it is not normal. If the home has a pressure regulator or back flow preventer and it does not have an expansion discharge valve or an expansion tank this is why it is leaking. Also high water pressure can cause them to leak.

[Rick Cantrell]

Scott has the right idea.
I think it should read
It is normal (but not correct), if the home has a pressure regulator or back flow preventer and it does not have an expansion discharge valve or an expansion tank, this is why it is leaking.

[Chip O'Brian]

As others have said, it is not normal. If the home has a pressure regulator or back flow preventer and it does not have an expansion discharge valve or an expansion tank this is why it is leaking. Also high water pressure can cause them to leak.

This property does not appear to have either.

[Rick Cantrell]

Chip

As the water heats up in the water heater it expands. A backflow preventer and pressure regulator stop the water from expanding back into the city water line, and the expanding water increases pressure, therefore an expansion tank is needed to allow the water a place to expand to and thus reduce pressure. If there is not an expansion tank, then the pressure will build up, the T&P valve will open to relive the pressure.
So either the T&P valve is leaking because it's bad, or it's leaking because there is not an expansion tank. Either way it should not be leaking.

[Jerry Peck]

As the water heats up in the water heater it expands.


expanding back into the city water line, and the expanding water increases pressure, therefore an expansion tank is needed to allow the water a place to expand to and thus reduce pressure. If there is not an expansion tank, then the pressure will build up, the T&P valve will open to relive the pressure.
So either the T&P valve is leaking because it's bad, or it's leaking because there is not an expansion tank. Either way it should not be leaking.

Does not even need a backflow valve or a pressure regulator, which is why the expansion tank is required (or, according to some plumbing inspectors, a pressure relief valve - I don't buy it, but I'm busy with the T&P drain discharge outlet first, then back to the thermal expansion tank issue).

You should be finding at least another pressure relief valve (besides the T&P). The T&P pressure relief is set to 150 psi, which is WAY TOO HIGH for the maximum allowed 80 psi, so the other pressure relief should be set to no higher than 80 psi (P2903.3.1 FRC), and this will 'leak' whenever the pressure gets too high (above 80 psi).

[Rick Cantrell]

Jerry
I don't follow what your are saying.
"Does not even need a backflow valve or a pressure regulator, which is why the expansion tank is required (or, according to some plumbing inspectors, a pressure relief valve - I don't buy it, but I'm busy with the T&P drain discharge outlet first, then back to the thermal expansion tank issue)."

[Jerry Peck]

Rick,

You don't need a pressure regulator or a backflow preventer valve to create enough pressure in the system to cause the T&P to leak. While it takes 150 psi to make them pop open (at least that's what they are set at maximum), they will 'leak' at a lower pressure.

That's all I was saying.

The rest was for Chip as he is in Florida and I was just stating that I'm trying to convince those-in-power that flooding the house when the T&P goes off serves no practical purpose - when the T&P goes off, it has passed through its danger zone and gone into the safety zone, just like it would do when draining to the exterior - like was done for decades. Meaning, I'm not beating people over the head about thermal expansion tanks yet. :D