Finding a water leak - looks like a really tricky one!

[Dave N]

Looks like we could be in just about the worst possible situation for a leak.

We started hearing running water in the cold water feed a couple of days ago, and have confirmed that it's between the stopcock in the street and the one in our house. I've also done a simple leak test dipping the kitchen tap in a glass of water and turning off the stopcock in the street, and you can see the water level in the glass falling quite fast.

The nightmare is that we're in a Victorian terrace with a shared supply that comes through next door and feeds 4 houses from the back, and no one has access to under their kitchen floors. We are in the middle of the line between the feed and one other house. And we've looked under the suspended floor next to the kitchen and confirmed that the floor void has been concreted over rubble, so there's no chance of access from below. And the shared supply means that running a new supply probably isn't feasible either.

Our insurance company isn't interested until we can see visible damage so this isn't covered (yet, anyway). We can only hear the water in our kitchen, not in our neighbours' kitchens so it's likely to be under our property, but we can't be absolutely sure of this.

So...any good suggestions for diagnosing where the leak is, and perhaps persuading our insurance company to do something about it? Thanks :)

[N_Cook]

Make a listening stick from a steel rod with a large wooden drawer knob fitted to one end, for placing your ear against. A skilled human leak detectector can narrow down the disance to the leak quite closely. The principle is high frequency hiss the leak is near to you and low pitched rumble is at a distance. How long it takes to gain the required skill, I don't know.

[Tim Lamb]

In message [e-mail], Dave N [e-mail] writes

The water engineers here have used a wooden rod with a cup turned at one end to listen for the leak. I don't know if the microphone on a mobile phone could be utilised.

[Dave N]

Thanks for the suggestions - yes, was looking at making a listening stick and that looks like a good starting point. Any more suggestions for tracing the pipework would be welcome. the other thing I'm trying to find out is where the rising main is in each of our neighbours' kitchens, but two if them are away this weekend so I'll have to wait. Ours and next door on one side are both against the rear wall of the kitchen extension and if the other two are as well that would give a starting point as to where the shared pipe is likely to run. However, a neighbour further down the terrace has her rising main further into the extension, and two friends in a nearby terrace have theirs near the back of the main part of the house. At least we aren't on a meter (I think it would be pretty hard to fit one here anyway, although we keep getting letters about installation it never actually happens) and if we got one it would have to be fitted downstream from the leak unless the water company would like to fix it for us. If the pipe does run along the back wall we could possibly access it by removing bricks rather than breaking the floor, which would be less destructive. In any case it would be very helpful to identify where the leak actually is first. Please do keep the ideas coming!

[Paul]

Our guys have an amplified one, a pickup disc that lays on the street, and a pair of headphones. That helps cut down street noise. It's not really all that fancy. The disc is waterproof, and they like to put it in puddles.

Paul

[Robin]

Check with your water company. Your and your neighbours are responsible for the supply pipe. But the supplier may be able to help. At the very least they may help persuade your neighbours it's their problem too.

[Thomas Prufer]

This came up in a German electronics newsgroup: A group of houses was supplied by a mile or so of plastic pipe, owned by the householders. Leak in the pipe, under asphalt so not heap to "just dig and make good".

Someone built a ground microphone and got to within feet of the leak. Electronics were mostly bought, bit of chickenfeed around a bought circuit board. Microphone was a piezo beeper disc with a weight and a brass pipe fitting.

Thomas Prufer

[Davidm]

As the leak is after the street stopcock your water company is not responsible for it, but they might (should) have an interest in conserving water and might send someone out to help identify where the leak is. Worth asking them. It worked for me a few years ago. The engineer they sent out not only found where the leak was but put me in touch with some guys who came out and fixed it (new pipe). Cash in hand job, they were contractors who were used by the water company, so had all the right equipment.

[N_Cook]

The next tool in the arsenal is freezing. When you gain access to the pipe at some point midway, to test whether that point is before or after the leak. Traditionally freezer solution of crushed ice cubes and salt in a cutdown plastic milk bottle made into a trough around the pipe. These days a can of aerosol freezer spray. When the supply to your house stops, is there still hiss at the test point or not. Often these days leaks are due to excessive number of Asda/Ocado/Prime/UPS vans parking on the pavement, then the leak is outside your curtillage , so then the utility companies pigeon.

[Tricky Dicky]

Where several properties share the same sewer pipe then the water company is responsible for the sewers to each property, is this not the same for the water supply? If it is the residents responsibility then as you all share the same supply I would imagine it is everybody’s responsibility to fix it, particularly those past your property as their supply would be affected by the leak on your property.

[alan_m]

A fiver for a smart phone (hands free) microphone, mount it in something like a sink plunger to isolate it from background and a free app on the phone to analyse the audio.

[Robin]

No.

If it is the residents responsibility then as you all

It is a joint responsibility (subject I think to anything in the deeds) but getting everyone to pay is not always easy. One benefit of getting the supplier to do the job (if they offer that option) is that they may (a) require everyone to sign up to pay their share and (b) take on the job of chasing for payments. Depending on your neighbours that can be well worth a higher price than cash-in-hand contractors.

[nothanks]

Report it to the water company who will check and confirm the leak. They should also base water charges on usage that existed before the leak was reported, so you won't pay for the lost water. Some companies will repair one leak FOC so speak to them and apply a bit of persuasion. I managed to get my water company to repair a leak in the supply pipe but a year or so later decided to pay for a new pipe to be mole'd in when it failed again.

[Animal]

I'm not sure why you want to find the leak in a rotten pipe you can't access. Replacement would make more sense.

[Thomas Prufer]

The guy that built the piezo sensor tried an electret mike first, with disappointing results.

Thomas Prufer

[N_Cook]

A critical point is repeatably consistant acoustic coupling to different sorts of pipe to then use an audio spectrum analyser app to get some sort of distance to leak value.

While on this topic. For tracing the path of a pipe that must have been laid to avoid a tree that had long since gone as in a loop. I used a low power RF signal generator with output connected to an exposed length of the known pipe run and tracked with an ordinary AM MW

+LW radio , giving a whine on the speaker.

[Dave N]

Thanks for the suggestions - here's an update...

1. I've made a simple listening stick from a steel stake that we had in our garden and a wooden door knob, and it seems to work. I also tried a small electret microphone on the end of my listening stick, with a laptop and earbuds, but the set-up wasn't sensitive enough to pick up the sound.
2. I still need to go round and see next door where the common pipe appears to come in from the street (they have been away), to attempt to ascertain where the shared pipe runs. My initial listening indicates that it could be about 0.5-1 metre from the main part of the house into the extension, but soundings and looking at their rising main might help.
3. There seems to be a slight increase in volume and pitch of the noise that I hear with my listening stick near the party wall where I think the supply could come in from next door, so there's still a chance that it's next door, but the noise is much louder near the far corner where the rising main comes up in our kitchen so I'd say this area is most likely. But of course exposed pipes and a pipe coming up through the concrete are likely to sound louder anyway so this isn't certain.
4. Our water company's website seems pretty emphatic on where responsibility lies, with clear pictures. In fact it states that if you report a leak on your premises to them they will take enforcement action if you don't fix it, so I'm not sure whether contacting them will help me at all.
5. Our buildings insurance covers trace and access for leaks as well as repair, but they aren't interested in any kind of claim until there's any visible damage.

So it seems we are still on our own here unless we start getting a significant damp problem or subsidence. All I can do is narrow it down as much as I can and presumably eventually work out where the best place will be to break up the floor, paying for a specialist leak investigator if necessary. Not ideal!

[Thomas Prufer]

The guy that built the piezo setup posted in de.sci.elctronics:

The pros had failed to find the leak using two microphones and a correlation setup, on a run of 150 meters under asphalt in 40 mm plastic pipe.

He's flown a drone over the run, on the chance that the plants might be visibly greener (in a hot summer) near the leak.

Other suggestions for the scenario that led to the piezo setup (where Rf wouldn't work -- plastic pipe) were:

- take resistance measurements between the water in the pipe and the ground, along the presumed pipe run -- nearer the leak should show lower resistance.

- blow helium in the pipe and use a helium detector

- blow compressed air in the pipe and use a microphone/listening stick as the leak would be/might be louder

- dig up the middle, install a valve, and see if the leak is before or after, repeat.

Thomas Prufer

[N_Cook]

Then there is water diving, just needs a couple of bent bicycle spokes in some bits of bio pen, worth a try.

[Tim+]

If you’ve not noticed a problem up till now it’s probable that the water has found it’s way into an existing drain. This happened to our neighbours. Lifting a manhole or two and looking to see where the water is leaving may help in locating it.

Tim