Relief valve(?) over utility sink leaking

ink · 11-30-2011, 09:50 PM

The utility sink has this branch and valve over it.

It's in the rental house. The tenant said it's been dripping and getting gradually faster, and now it's going at the rate of a slow faucet.

Before I just go and cap this thing, I figured I should find out what it's for and if it's needed. At a guess, I'd say it's a pressure relief valve? Working on that hunch, I gradually closed the water main. At no time did the water stop coming out of the valve, though. So if it is a PRV, then either it's not working anymore, or slowly closing the main doesn't effect the pressure enough to change what it's doing.

Any help is appreciated!

Thanks.

joecaption · 11-30-2011, 09:57 PM

Unless there's a hot water heater under that sink there's no reason I can think of for it being there.
Water lines do not need a pressure relief valve.
Hot water should be on the left not the right so if it's the cold water side then just cap it off.

Billy_Bob · 12-01-2011, 12:24 AM

It's there for a reason!

Is there a boiler in the house?

Hot water heater and that is the pressure relief for that instead of a T&P valve?

Perhaps the hot water heater needed an expansion tank and that was installed instead? In that case it would leak water when the water heater is heating. Heated water expands and needs to go somewhere!

http://www.lower-my-energybill.com/w...sion-tank.html

joecaption · 12-01-2011, 08:28 AM

Just look to see where it goes, if it's connected to the cold water side of that sink, and feel if the pipe is hot, if not then it's not a boiler relief or a water heater safety valve.

ink · 12-01-2011, 01:17 PM

Thanks, guys.

It's the cold water side. The water feed splits from a 3/4" and one half feeds the electric HWH while the other feeds the cold side of the sink and the washing machine. The split above the sink is between the HWH and the sink. The HWH is out of frame of the picture directly to the right.

There is no boiler; all electric house (heat pump).

I agree that it was put there for a reason, but I don't know what that reason might be. I recently replaced the HWH, as the old one was on it's last legs. The install was done using the existing plumbing, though, so that shouldn't have changed anything. Any chance this was SUPPOSED to be an expansion for hot water but just was put in the wrong place at construction time?

Thanks!

joecaption · 12-01-2011, 01:20 PM

The new water heater should have it's own relief valve, so that old one is not needed anymore.

ink · 12-01-2011, 01:21 PM

I need to expand on the first post.. it's a bit deceiving. When I closed the water main, the water coming out of this valve SLOWED, but never stopped (as I would've expected if it was pressure-controlled). If I closed the main entirely, the water would gradually come to a stop, of course.

Ironlight · 12-01-2011, 01:44 PM

If you gradually close the main valve that thing would continue leaking until the main valve was completely shut as your system would continue to have pressure until the main was fully closed.

Shut off the main, open the cold water in the sink to drain that branch, and cap it.

Billy_Bob · 12-01-2011, 01:56 PM

Was the water heater running when you closed the main water valve?

When water heats, it expands. That builds up the water pressure if there is a "check valve" at the city water meter or a closed main valve.

Ask your water department if they have check valves at the water meters. If yes, you have a "closed system" and would need an expansion tank for the water heater or that existing pressure relief valve.

If there is no check valve, then as the water heats, excess water would flow backwards through the water meter - relieving the pressure.