Gas water heater Pressure Release Valve and Extra Hot Water

[reissgirl]

I have a 2004 Whirlpool GAS hot water heater. Last night my water seemed hotter than usual. Two hours later I noticed my water heater's temperature & pressure release valve was leaking. I replaced the T&P valve about 24 hours after noticing the leak. The water temperature was almost instantly back to normal and it's not leaking. I'm concerned that the leak was actually caused by a faulty thermostat. It's been a few hours since I replaced the T&P valve and the water temp feels stable (I don't have a thermometer). Could a faulty T&P valve cause the water to overheat? Or does that definitely indicate a faulty thermostat or corroded element or other? I know the unit is old but for now I want to make sure my basement is not going to flood any minute.

How can I confirm that the new valve resolved the issue? I'm worried it will leak overnight and I won't stop it as quickly as the first time around.

 

[Jadnashua]

The T&P valve has nothing to do with the thermostat on the WH. It is a safety device that will open to relieve excess pressure or high temperature, at 150psi or 210-degrees F.

The more common problems with them is getting old and mineral deposits that might prevent them from opening when they should, and not closing fully, if they do. The next big thing is if you have a closed system and a failed expansion tank. The easy way to check an expansion tank is to just tap on it...it should primarily be full of air so will 'feel' light, and ring if you hit it with something hard. If it is heavy or sounds dull when hitting, it's probably waterlogged, and needs to be replaced.

 

[Sponsor]

 

[reissgirl]

I don’t have an expansion tank. I know the T&P valve was doing its job when it leaked. I’m glad it did! Can it fail in a way that could cause extra hot water? Why did replacing the valve seemingly fix the problem? And why was the water instantly hot after the unit had been shut down for 24 hours?

 

[Jadnashua]

Because of the insulation, unless you drained the tank to replace the T&P valve, the water can stay hot for a long time. While not quite the same thing, my indirect WH provided me with a hot shower for three days while I was trying to get my boiler fixed. THey're different (closer to an electric) in that they don't have a flue going up the middle like a gas WH, but still, there is insulation in there to help slow heat loss.

The T&P valve has NOTHING to do with the control of the thermostat or heat generation in the WH...it is a safety release valve to protect things if they go bad for some reason. There is NO physical connection between the WH controls and that valve.

If the utility company has done any work on your supply lines or meter, you may now need an expansion tank whereas it may have worked fine without one for years. Where I live, they are required by code, but there are probably a large percentage of people without one. As things get upgraded, they will have problems unless they have one.

Just thought of one other possibility...if you have a tempering valve on your WH, it may have failed and is letting super hot water out. WHere is the thermostat set? Many of them no longer have degrees marked on them, but the further up the alphabet you go, the hotter it's trying to make the water.

 

[hj]

if you have a gas water heater, you do NOT have an "element".

 

[Reach4]

And why was the water instantly hot after the unit had been shut down for 24 hours?

That is not possible for a tank type water heater, unless we presume something unusual such as you having two or more water heaters.

 

[reissgirl]

That is not possible for a tank type water heater, unless we presume something unusual such as you having two or more water heaters.

I shut the water and gas to the HW heater. 24 hours later I turned it back on and the water in my sink was hot. We only have one unit. Sounds like it was well insulated. When the unit was shut down no water came out of the faucet when turned to hot so it wasn’t used up I suppose.

 

[reissgirl]

Another 24 hours have passed and all is working well. I didn’t feel the increased temperature - my husband commented when he was doing the dishes about 2 hours before we found the leak. Maybe he was mistaken about the extra hot water but it’s doubtful. I assumed that the thermostat was broken and the water got hot enough to trigger the T&P valve to release. Replacing the valve has seemingly fixed the problem but that doesn’t make sense to me if the water was so hot. It sounds like the valve was working properly if it was draining. The thermostat was set one notch above the recommended line, and has been for several months. I’m assuming the recommended line is 120 degrees and the next line is 130 degrees. Now it’s set at the recommended line and the water temp is stable. I can’t rest easy though because I don’t understand how replacing the valve would rectify the increased heat. We have a smart water alarm coming tomorrow!