hot water heater - hot water venting outside from mixer valve
 

Hi,

I have a gas powered water heater tank that is continually leaking hot water outside via what I think is an overfill pipe. Having looked at diagrams online, I think it is coming from what is called the mixer valve (please see photos below). I originally thought it was coming from the pressure relief valve (PRV), but that is a separate plastic pipe and is not leaking. Note that I have two vent pipes to outside, one from the PRV and a second from this "mixer valve" thing.

I did test the pressure relief valve and it seems to be working fine. Flows when I open it and stops when closed. When I do operate the PRV, the venting of water from the "mixer valve" stops for a minute then starts dripping again to outside via the plastic pipe. It is a vigorous drip, maybe a few gallons per day. We have no complaints about the volume or temperature of our hot water.

The water heater is 13 years old and despite having the manual, I do not know what manufacturer it is. There is no ID on the manual, not even a name. We live in a soft water area (N Atlanta) and this heater is the original install on a 1999 house. Note that there is a continual ssshhhh sound like a faucet is running and it is coming from this valve (please see the last photo for closeup of valve).

I was hoping it was an issue with the PRV and maybe it is - I know little about water heaters.

Thanks for any help.

http://mcontact.bestmail.us/DSC_0475_new.jpg

http://mcontact.bestmail.us/DSC_0471_new.jpg

http://mcontact.bestmail.us/DSC_0474_new.jpg

And the valve close that up :
http://mcontact.bestmail.us/DSC_0478_new.jpg

That's not a mixing valve. If it were a mixing valve it would have 3 pipes attached to it. 1 pipe would be cold 1 pipe would be hot and one would be the mixed water. That looks like some kind of back flow preventer though I haver never seen or used that style so I'm not 100 percent on that.
Does it have a cold pipe going in and cold pipe coming out with a vent on the bottom? I can't tell by the pics.

Thanks for the reply cjn79.
It has only two pipes in total. It has a single hot pipe coming in from below (that pipe comes from the hot pipe heading into the house). The second pipe is the plastic vent pipe going to outside.

Never mind I don't believe it's a back flow preventer. It actually does look like some kind of relief valve but like I said I'm not familiar with that style.

I live in Maine so we don't vent anything to the outdoors because it would obviously freeze.
Ya if it has a vent it more then likely a relief valve. Call your local plumber and see if its required to have a relief on the hot side as well as the one on the tank. That is not required in Maine so if its not required where your at you could cut the relief out and cap the pipe seeing how there's one on the tank already. But check local codes first.

Or you could have your plumber replace the valve for you.

I think you are right, it some kind of relief valve. The top part of the valve has a calibration scale etched into it and the name "WILKINS" etched in. It has marks like 1500 then lower marks of 175, 150, 125. All those marks are etched on a nut that looks like it could be adjusted with a T screwdriver vertically from the top.

Going to need a plumber on this one.
Thanks

Left it to the wife to find the serial number and Manufacturer. The tank has a label "state select" and serial # PR6 5C NBRT971.

Ya you shouldn't need the numbers as it is not part of the hot h20 heater. Your plumber may have it in stock or may have to run to the supply house but either way relief valves are a simple fix.