Currently reading:
Pressure Relief Valve Behind Washing Machine Problem

Discuss Pressure Relief Valve Behind Washing Machine Problem in the UK Plumbers Forums area at Plumbers Forums

Hi, all. I have a leak problem behind the washing machine. It's a pipe that is leaking directly into a drain. It used to drip but now is leaking a steady stream without stopping.
Seems to be coming from water heater but I cannot tell. It is cold water. When I turn off the main water supply, it stops.

The image below shows a connection in that pipe. Seems to be a pressure relief valve (PRV) but I cannot tell because it doesn't have any way to adjust the pressure. I capped the leaking pipe with a Shark-Bite and the elbow (the PRV) started shooting up water. So I took the Shark-Bite off.

Question is why is the PRV there behind washing machine and what purpose does it serve? And why did they put the drain there?
I haven't replaced the PRV yet because I can't find an exact type. The one I found has a way to adjust the pressure and I'm not sure what pressure it is supposed to be set to.

The "leaking" pipe is the discharge from a Pressure Relief Valve for the water heater that will be fixed to the heater. (either gas or electric). Not the valve in the box in the photo.

It's behind the washing machine so that you can see there is a problem.
You appear to have already noticed there's a problem but not had it looked at.

If the PRV has been discharging for some time it will need replacing but not before the problem with the water heater is fixed first.
Hi, snowhead. I appreciate your response. However, here is what is baffling me. Please see video of my water heater setup.

I have a drain pipe at the water heater that forks into a T. One end of the pipe goes down to the floor as like most water heaters I've seen and you have to put a bucket to see it leak.
However, the T in the drain pipe goes up to ceiling and I'm assuming ending up in the laundry room which is right above it.

But the end which ends up on the floor near the water heater does not leak at all, whether the cutoff is open or closed. Only the end that ends up in the laundry room leaks.

That's most odd.
Firstly that there's a valve / cutoff in the discharge from the Pressure relief / safety valve, that wouldn't be permitted here in the U.K it has to be unrestricted.
Secondly that there is the other pipe rising away and possibly leading to the leaking pipe.

Is the pipe rising from the water heater warm, suggesting flow in it, if so the pipe to the bucket may be intentionally plugged to force the flow upwards?

It may be that the rising pipe is the downward discharge from another water heater or something else above??

I thought it was a reasonably simple issue as although I'm in the U.K my Son lives in Arizona and has a water heater with it's safety valve discharging to a pipe through the wall to the laundry room water / waste (drain) box just like yours appears to.

When you turn off the main water supply, is that to the whole house / appartment or just to the water heater?
Thanks for your response.
1) I am not sure if the water in the pipe rising from the water heater is hot/warm. The pipe doesn't seem to be hot. If that is the source of the leakage in the laundry room pipe, then the water that is leaking is not hot. It is actually cold.
2) The pipe to the bucket, the discharge pipe, is not blocked. Because when I test the pressure relief value by releasing the pin, the hot water gushes out into the bucket, when the cutoff is open. When the cutoff is closed, the water does not gush out in the the bucket, nor does it gush out into the leaking pipe. The leaking pipe just leaks away at the rate it does. When I open the cutoff, then the water gushes out into the bucket. It's like the water is held and pressure builds up in the water heater when I release the pin with the cutoff closed.
3) I only have one water heater in the house. There is no other. My A/C runoff goes outside the house. And the A/C is off this time of year.

This is the reason I believe the source of the leak is not the water heater PRV. But I cannot think of anything else in the house.

My thought was that this pipe comes off the water main and maybe there to detect if the pressure regulating valve might be damaged and needs replacement. But I've never heard of such a thing.
Last edited:
Download this

Then pull that white vent looking cover off your laundry room wall. You will probably see this auxiliary pressure relief valve or something very similar. I'm dealing with the same issue myself. Took me forever to figure it out.
Yes, I have this as well.

I called a plumber. He said this was not according to code. The builder, instead of installing an expansion tank on the water heater, took the cheaper method and installed this instead. So, we just let the plumber cap this off and let him install an expansion tank on the water heater.

New Threads

AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock