What a shared water supply pipe leak means
A shared water supply pipe leak is a leak on a buried pipe that feeds more than one home before it splits. The shared length is usually the joint responsibility of every owner it serves; each branch to a single house is normally that owner's alone. The leak is found by testing with every home on the pipe, closing each stop tap in turn, then listening along the buried route.
Shared supplies are often found in older terraces and pairs of semis, where one pipe was laid along the row and branched off to each house. They also turn up on shared drives, in farm cottages fed from the farmhouse supply, and in houses split into flats. The leak may show itself as a letter to one household, a wet patch in someone else's garden, or weak pressure for everybody.
How to tell if your supply is shared
Start outside. Look for the small covers in the pavement or front gardens that hide each outside stop tap or meter. If there are fewer covers than houses, some homes may be sharing a pipe. Indoors, the clues are pressure that drops when next door runs a bath, or a supply pipe that comes into your house through the wall you share with them. Your deeds or title plan may also mention a right to run water pipes through a neighbour's land.
If you are still unsure, ask your water company. It may hold a record of how your home was connected, and it may be able to tell you whether your meter, if you have one, measures your home alone or several homes together. That matters later, because a meter covering the whole group is the simplest way to check the shared length for a leak.
Who is usually responsible
Your water company generally looks after its main under the road and its short pipe up to your boundary. In practice, joint responsibility for the rest means the owners agree between them who organises the search and the repair, and how the bill is split. A leak that sits under one person's garden or drive does not usually make it that person's problem alone. Your deeds may set out a different arrangement, so check them before anyone agrees to pay a share.
If you are a landlord, the job is normally yours to arrange rather than your tenant's, even when the letter arrived in the tenant's name. Tenants on the pipe can help on the day by letting us in and keeping their water off, but the decisions about the search and the repair sit with the owners. If the owners cannot agree at all, a solicitor can tell you what your deeds say about the pipe.
Why testing needs every property's help
A water meter only tells the truth about a leak when nothing it measures is using water. On a shared supply, that means every home at once: no washing machine halfway through, no shower, no toilet refilling next door. Each stop tap on the pipe also has to open and shut properly, because the test depends on closing them one after another while somebody watches the meter.
Listening needs the same quiet. The sound of water escaping from a buried pipe is faint, and a dishwasher running two doors along can drown it out. We also need to reach every stop tap and outside cover on the pipe, and because a shared pipe runs to or under a neighbour's property, mention that when you book. Settle these points between you before you ring:
A time when no home on the pipe uses water
Who books the visit and who pays us
How the cost is shared between the homes
Who will let us into each house
Who can approve a repair if one is needed
Finding which length is leaking
Where one meter measures the whole group, the first step is a process of elimination. With every home quiet, each indoor stop tap is closed in turn while someone watches the meter. If it stops when one house shuts off, the water was going somewhere inside that house. If it keeps turning with every indoor stop tap closed, the leak is underground, on the shared length or on one of the branches.
Next, a ground microphone goes over the buried route, the shared length first and then each branch, listening for the place where escaping water sounds loudest. Plastic pipe carries sound poorly and a small leak is quiet, so on those we put tracer gas, a hydrogen and nitrogen mix, into the pipe and pick it up at the surface where it escapes. A different method has to agree on the position; once it does, we mark the spot and photograph it.
Where each home has its own meter on its own branch, a leak on the shared length may not register on any of them, because the water escapes before it reaches a meter. Then the clues are wet ground or falling pressure for everyone, and listening and tracer gas do more of the work from the start.
Shared pipes and our home water leak promise
No find, no fee on home water leaks does not cover shared water mains. Full conditions are on our terms page. So a search on a pipe you share is priced like any job outside the promise: the price we agree is charged whatever the outcome. The fuller the picture you give us when you ring, the better we can plan the visit and the more accurate the price.
The price is settled by phone or email before we put the visit in the diary. It is for our time, capped at either a half day or a full day's searching, and which cap applies depends on how long the pipe is and how many homes it serves. An early find does not bring the price down. Anything we spend on materials, parking or tolls is passed on at cost.
What happens after the leak is found
Once the spot is marked and photographed, you know which length is leaking, and that is usually what settles who arranges the repair. The written report gives the location, methods, readings and photographs. It goes to whoever booked, after the visit is fully paid, and that person can pass it to the other owners. If anyone is claiming on a home policy, check first whether it includes trace and access cover; the insurer decides whether to pay.
If the neighbours want the shared pipe mended there and then, we can usually do that, priced separately from the search. A repair price we give ahead of time only holds if the pipe is fixed while we are there on the day of the detection, so agree in advance which owner can give us the go-ahead. Our repairs are guaranteed for 3 months from the day the work is done, and that covers the new joints and pipe we add, not the rest of the shared run.
Old, worn pipe can give way at a second weak spot once it is tested or mended, and fixing that would be quoted as a separate job. Some neighbours use the moment to ask the water company what giving each home its own supply would involve. If the leak first came to light through a letter from the water company, tell it when the repair is finished and ask whether it offers any allowance for the water lost.