Hissing noise from pipes but no leak?!?

13 Oct 2004
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United Kingdom

For the past 3 weeks I've noticed a sort of hissing noise from the water pipes all over the house (not central heating). Its the sort of noise you get if a tap is half turned on - hissing isnt the right word. Bascially it sounds very much like water is running through the pipes.

The pipes run from behind the washing machine in the kitchen (great place for a stopcock), up the kitchen wall beside the combi bolier, along the landing to the bathroom. I can hear the noise from behind the washing machine, around the boiler, along the landing, in the bathroom, basically anywhere there is a pipe.

I've tried switching off the taps to the washing machine thinking a recently installed new washer was the cause, but it makes no difference. I can find one leaks or evidence of leaks throughout the system.

What on earth is causing this noise?
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You may have a leak somewhere you can't see (like under the floor)

If your house is 50 years old or so and has steel pipes for the incoming main, they may well be holed. This can happen even if they are buried in a concrete floor.

One of the places they erode is at the elbow where the horizontal pipe turns vertical to come up through the floor.

The floor is likely to be damp near the pipe.

If you turn off the stop-cock in the kitchen, and the noise stops, it is inside the house.

If it doesn't stop, but does when you turn off the stop-cock in the pavement or garden, it is probably under the floor.

If it doesn't stop even then, it might be your next-door neighbour, especially if you are in a semi or terrace.
The house is 134 years old, the kitchen floor is concrete, and I have been struggling to work out what is causing damp on the back wall of the kitchen.

Would I not eventually see some evidence of the leak on the kitchen floor? By the sound of the pipes theres a fair amount of water shifting (running tap sort of quantities), and I can hear it 24/7.

I'll try the stopcock tonight and post results, but I can't see the leak being in the house because the pipes run from the stopcock straight up to the first floor, then along to the bathroom. I would have thought I'd be missing a ceiling by now.
You might not notice the leak on the surface. It may have been running for quite a while and washed away some of the foundations :cry: or found a crack for it to run away downwards :(

I had a leak under the concrete floor of a 1930's house. detected it by sound. The floor was relatively damp in that corner, but we had assumed it was due to splashing or leaking from the old sink (which also leaked).

Had to trench out the concrete floor.

If it is near an outside wall it might be worth exploring the wetness of the ground outside (you may need to dig a hole).
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The house is an end terrace. The stopcock is on the back wall. on the outside of the wall is some decking, constructed ontop of a flagged yard.

Digging isnt really an option I'd like to explore - I'm moving house next week, but I feel I need to try and resolve the sound before moving.

The sound is not coming from a neighbouring property (pipes and kitchen are not on walls that adjoin another property).

I'm not sure I have the ability to turn off the water from outside the house - theres a metal mains cover outside my back gate - dont think I have the tool required to tamper with it.

Thanks for the replies. I'll report back this evening after switching off the stopcock.
do you have a water meter

if so turn of your main stopcock in the house if it still spins then its the main
As the house is so old I don't think this really applies, who knows? I had a customer that reported a loud hissing noise in the cupboard under her stairs where the rising main entered the property, we eventually tracked the noise down to a leaking external stop valve 12 Metres away from the house, the reason why we think it was so loud was that the pipework was sleeved and the noise was travelling along the water in the sleeve. It was a real hissing sound just like the leak was right next to you so the sound as we know travels quite a way under water. We assumed the sleeve was full of water and the noise just got amplified in the cupboard some how. there was no signs of damp anywhere, it really was quite odd but one we all learned from.

true ididididi
might not have a meter, kinda why i asked m8 ;)

turn off the mains at the road stopcock and see if you can still hear it
Sorry Corgiman I was referring to my post might not apply as it would be unlikely that the pipework would be sleeved so the noise would not be amplified.

Cheers M8
Sorry, I've managed to take a week to come back to you.

Not got a water meter.

I turned the stockcock off, and the noise can no longer be heard in the bathroom or upstairs, but is still there in the kitchen - from the stockcock and down under the floor.

At the rate it sounds like its running I would have thought the side and back alleys would be full of water - its been going for a good 3 weeks now. No loss of water pressure inside the house from what I can tell, but its always been quite high (4/5 bar) so am not sure I'd notice a difference.
If it is leaking under the floor, it has probably washed a channel down through the foundations, and will continue to wash them away, especially if you have soft bricks and lime mortar.

Time to hire a Kango, I think.
Well it seems like you need to renew the pipe from the water board`s stopcock in the path .........to your house :cry: Worth a call to them to acertain if the tap is working.......then dig a trench 2foot6 deep and lay a new blue MDPE pipe..that`s the cheap bit ...but you`re moving .......bit of a dilemma :cry:
Well, next steps - I'll see if I can work out where the external stopcock is and turn it off. If it is the case that the mains pipe is knackered, do we think my home insurance will cover it? I'd expect the decking will have to come up, parts of the kitchen may have to be moved. Just want I need 3 weeks before moving.
To check for a leak in your supply pipe,

Turn off their stop valve
Hold a tumbler of water up to the spout of an open cold mains tap (kitchen, say).
If there's a leak it will suck water out of the tumbler. Joy that the trick works is quashed by the estimate for repair...

You have to give a bit of thought to the water in the house's pipes though. If you wait until the wc and loft cisterns are full, and open the kitchen tap and nothing comes out, the test should work OK.
You may have to force a seal at the cistern inlets by pouring extra water into them, otherwise the leak will suck air in.

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