TPR Valve still dripping HELP!

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Geraldo

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I noticed my hot water heater TPR valve leaking so I replaced it. It was still leaking after I installed the new valve. A plumber suggested I replace my water heater which I did and the TPR valve is still dripping. I checked the water pressure coming into the house and it's at 70 PSI which the local water district said was normal. Another plumber suggested a thermal expansion tank or pressure regulator. Problem is, no one else in my neighborhood has this problem. any help or suggestions would be greatly appreciated.
 
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Gary Swart

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TRP valve

Replacing the entire tank because the TRP valve was leaking, is about as logical as buying a new car because a radiator hose was leaking. There's nothing about the tank itself that will cause a valve to leak. Sure, if the tank is defective and overheats, the valve with pop off, that's what it is intended to do. I know you replaced the valve before you replaced the tank, but a new valve can be defective. Would have made more sense to try a second replacement valve. You've got the new tank now, so that's a done deal, but before going to more expense,my advice is to try another new valve. The expansion tank would be an excellent addition, they are required now in many places. The pressure is a bit higher than necessary, but a pressure regulator isn't expensive nor hard to install. I don't think either of these will have an effect on the leaking valve.
 

Jrejre

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Maybe you're just unlucky and got a new water heater with a defective TPR valve. For under $10, I'd consider just changing the TPR and see if that does the trick.
 

jadnashua

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You might have a check valve in your house and not necessarily know it. I think that I heard that some water meters have them in them now (don't quote me on that!). So, if your house water system is now "closed", as the water heats up, it expands and can't go anywhere so the valve opens up momentarily to relieve the pressure. Stops until you run water out of the hw heater, replacing that expanded hot water with denser cold water which heats and expands, and it happens again. This could happen if they replaced your water meter for some reason, or there was some other work done which required your house to be upgraded to the new code. Closed systems are not required everywhere as I understand, but aren't a bad idea.

TP valves open if either the temp exceeds the upper limit, or the pressure does. I'd double check the pressure while it is happening. Your static normal pressure could be within limits, but after say a bath or a long shower (wash clothes with hot), then let the system reheat all of that water, and if you have a check valve somewhere, the pressure can go up quite a bit. Since water doesn't compress, the pressure rises and pops the valve.
 

jadnashua

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Bottom line, when you have a closed system, without an expansion tank, you are putting a lot of pressure on your system after draining then reheating the cold water in your hw tank. Something has to give. It could have been the hoses expanding on your washing machine, or a small leak in a faucet or toilet, or who knows what that allowed you to work without one previously, but you obviously have a problem with exceeding the pressure of your T&P valve now. HOses get harder as they age (often), and maybe they are no longer the weakest link. So, the prescribed "fix" for this is an expansion tank. When you have a closed system, they SHOULD have put one in when built. You can do it now, or live with the valve periodically opening, and doing its job.
 

jadnashua

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No two houses, even built by the same builder to the same plan, are truely identical. A manufactured house made on an assembly line might be really close. So, what happens in one house is no guarantee the same thing will happen in another, especially since people don't react the same. You might have a larger hot water heater and regularly take longer showers/baths/etc that run it until cold. This simple fact, vs a neighbor being more conservative and only taking s short shower could be enough so that the expansion and resulting pressure increase doesn't trip their T&P valve. Your check valve may actually work better than theirs resluting in a perfect seal, theirs may leak - it doesn't take much - take a look at how much water comes out when it does leak - it is not a torrent, or if it is, it doesn't last long (that is my guess); maybe a few ounces?

Sometimes, it just is.

As I said, with a closed system, they invented the expansion tank, and one should have been installed by common design practices on your house because it is a closed system. The only way you could get long term reliable results without one would be if you had really low incoming pressure so the resulting rise didn't reach the appropriate level, or if you had a tankless system so there was no volume of hot water to expand unless you were actually using it with a valve open (at least those are the only ones I can think of off the top of my head).

Also, I'm not a pro, but there has been more than one person here recently that fought the situation like you, installed one, and it fixed the problem. A tripping T&P valve is common in a closed system without a pressure tank. Bad T&P valves happen, too. Have you had several in a row, possible, but not really likely. The cause and effect in your situation is closed system, no expansion tank. A (unlikley) bad T&P valve is probably not. I really like to know why about things, too. In this case, I'm satisfied - but I'm not you. You can keep looking, but my suggestion is live with it, add a tank since there should be one anyway, and if that doesn't fix it, then you've got a problem.
 
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