PRV leaking when water heater is is on

Hi all,

I have a problem with my Pressure Relief Value (PRV) leaking when the water heater is on. I also have a water tank expansion installed and was wondering what I could do to resolve this problem. So far I bought a water gauge from Home Depot and found that in the normal state the pressure is 58 psi. When I run the hot water from a faucet the pressure drops to 48 psi. When the water is begining to heat I turn off the faucet and the pressure increases slowly all the way to 150 psi and the water starts to leak from the PRV.

One winter when I went out of town I turned the water heater to vacation mode and turned the water off from the main valve. I don't think this is the problem since it didn't start to happen until a year later. Any help would be greatly appreciated.

Thanks in advance.

Greetings kuldeep welcome to the Forum.

First of all, sounds like your PRV is working real good. Doing just what it's supposed to !

Just a few comments:
That 58Lb sounds high, residential right ?
Do you have a Check Valve in your main supply line ?
Problem is in the TStat or Elements of the Heater, what's your temp on the Water, with a normal setting ?
If it's Electric, have you replaced an Element since this problem started?

Have a good Day !
S.W>

Thanks S.W. for the quick response.

Yes it is a residential unit.
Not sure if I have a Check valve on our main supply but I suspect we do. It's a 5 year old townhome.

I need to check the temperature of the heater but was looking online for the best mechanism to do so (something similar to a water pressure gauge that you plug into the drain plug of the water heater to check the temperature).

It's a gas heater and I have not replaced the element ever. The heater is only 5 years old and this problem only happens during the winter.

Thanks again for any help. Will post the normal Temperature setting when I find out the best way.

Kuldeep,

Knowing those temperatures, and WHEN it changes is going to be a key to diagnosing your problem.

As far as checking the temp...
Simple is better. Get a Analog or Digital thermometer, go to the nearest Hot Water Outlet (sink/tub/whichever) and check it right there.
Of course let it run a sufficient amount where the maximum temp is reached, and note the pressure when the reading is made.

Just as a general rule, 120° is the recommended high for personal contact.

I'm not sure just why you wold have a Check Valve in your system. It may be that your Local Codes required it at some point, to keep from getting a Back-flow should the City Pressure source be compromised.

Today, most all communities require that Toilet Fillers and exposed Faucets have a Vacuum breaker installed in them, to keep from drawing (bad) water back into the closed system, should the source pressure be lost.

In any case, when you "lock" your system up with a Check Valve like you may have, there is NO way to keep it from a pressure increase like you're experiencing. Save for you turning on a Faucet, and dispelling the overpressure.

Seasonal use may cause you to do this inadvertently, thus your perception of the problem not occurring during the summer months. (Just a guess on that)

It's easy to attempt to focus on the Temperature Controller for your Heater, but, until you get your system where it will "breathe", you won't know if it's bad or good.

My recommendation is get rid of that Check Valve, then, reevaluate the situation.

Have a good Day !
S.W.

S.W. Here's an update.

Got a thermometer and checked the temperature when in the normal state. Water pressure 62 psi and water temperature capped out at 126 degrees F. Check the user manual for the water heater and found the setting to be at 120 degree F. Turned on the kitchen faucet until the heater kicked in. Watched the water pressure increase to 140 psi and water leaking out the PRV. When the gas shut off. I turned on the kitchen faucet and again measure the temperature at 133 degrees F.

At this point thinking that the Thermostat is operating correctly (if that's a safe assumption). I looked into the water expansion tank. Knocked on the water expansion tank with my hand and heard a sound as if the expansion tank is full of water. Turned off the gas and the main valve. Hooked up a garden hose to the drain pipe and released about 10 gallons of water. Pretty much until I felt the water expansion tank was emptied. Turned back on the water supply and the gas and as of 9 hours later, no problem with leaking (FOR NOW). But will keep you updated as the days goes on.

Couple of things I observed. I have a water regulator on the main water supply. Rated for 25-75 psi and says it should be set to 50 psi. After emptying the expansion tank the normal water pressure is 70 psi. Is this high? Will playing with the regulator decrease this?

Also I noticed that the water expansion tank is connected to the hot water supply line coming out of the water heater. The Rheem user manual clearly displays it should be installed on the cold water supply. Is this also a problem? Do I need move the expansion tank to the cold water supply side?

Thanks for all your advice and help so far. It's nice to know that I'm actually learning something even if I don't fix the problem.

Kuldeep,

GREAT UPDATE !

That expansion tank would have been my next focus. You still need to get some information on how it's "Charged".
You need to know if it has a "Bladder". Should there be any air pressure in it? Does it have a Air Filler Valve anywhere on it.
If not, I'd say drain it completely.

Get that Regulator set down to system pressure of 50# !
You're running to high, glad you found that thing !

I'd cut the Temp down a bit more if I were you, over 120 can hurt you !

On the placement of the Exp Tank...
It should work on either side of the Heater.
But, that's what makes me think it has a Bladder, the Mfg didn't want to expose that material to the higher temps.
This is just a guess, it may not have a Bladder, and you're ok then, with just draining it completely.

So...
Reset Pressure
Reset Temp
Drain/Charge Exp Tank
and...
I'd still find that Check Valve and remove it !

Have a good Day !
S.W.

My motto is to always start with the cheapest thing first. I would replace your PRV. It is a cheap part, easly accessible, and if that's not the problem, then go on to the next thing. The likelihood of any other thing being wrong with your system is pretty remote. You have a water heater. It works. you have an expansion tank. It is simply a tank with an air bladder in it. No reason for it to be broken. It is there to prevent over-pressurization of your water supply system due to expansion of hot water. No leaks anywhere but the PRV. Replace the PRV.