The line, drawn once
Four pieces of pipe, in order from the street:
| Pipe | Runs from | Whose |
|---|
| Water main | Under the road, serving the street | Thames Water |
| Communication pipe | The main to the outside stop valve at your boundary | Thames Water |
| Supply pipe | The outside stop valve into your house, to the internal stop tap | You |
| Internal plumbing | Everything past the internal stop tap | You |
Thames Water state it as: "We're responsible for the water mains that carry water around our region. We're also responsible for the communication pipe, that links your supply pipe to our water mains," and "As a homeowner, you're responsible for the water supply pipe that runs from the boundary of your property into your home." CCW put the same boundary from the other side: the supply pipe from your house to the property boundary, where the outside stop valve and meter are normally located, is your responsibility.
The stop tap is theirs, but it is still the boundary
This is the detail that generates most of the arguments, and it is in Thames Water's leakage code of practice. External stoptaps are apparatus belonging to Thames Water, installed on each service pipe to control the flow. They are usually in the footpath, though they can sit in a garden or driveway, and they must be positioned as near as reasonably practicable to the boundary of the street. Thames Water also hold a legal power to fit a stoptap to any service pipe, including a supply pipe, at their own expense.
So the fitting is theirs and the pipe on your side of it is yours. Owning the valve does not extend their responsibility past it.
Where the meter sits tells you nothing
Same document, and it is worth quoting because the assumption is so common: "Meters are also a type of apparatus belonging to us and are usually (but not always) fitted in the same location as the external stoptap. The position of the meter does not determine pipe ownership or responsibility."
In London the meter is frequently in the footpath outside a Victorian terrace, sometimes in a communal chamber for a whole row, occasionally in a basement. None of those positions moves the boundary. The boundary is the boundary.
Your pipe under someone else's land
Long shared driveways, converted terraces and rear-access gardens make this common in London, and the answer is not intuitive. Thames Water: "You'll also still be responsible for leak repair if your supply pipe crosses land belonging to someone else, such as a neighbour's property or the road." Their code of practice puts the endpoint precisely: where your supply pipe crosses land belonging to someone else, you are responsible for the pipe up to the point where it connects to their communication pipe.
So a leak in your neighbour's front garden, on a pipe that only feeds your house, is your leak. Access is then a separate problem, and a social one rather than a legal one, but the liability does not shift.
Shared supplies
A single supply pipe serving two or more properties is a shared supply, and Thames Water say it is "more common when buildings are close together, such as on a terraced street", which describes a great deal of inner London housing. Their position: you and your neighbours have joint responsibility for maintaining the shared part of the pipe and any associated costs, and each of you is responsible alone for the branch that supplies only your property. They add, flatly, that they do not get involved in third party disputes. CCW say the same: a shared pipe serving more than one property becomes the joint responsibility of all property owners connected to it.
That distinction between the shared run and your own branch is the whole game when the bill arrives, and it is worth a page of its own.
Telling whose side the leak is on, before anyone digs
The meter test
Thames Water publish this and it takes half an hour. Turn off your internal stop valve, usually under the kitchen sink. Make sure no cistern is refilling and every tap is off. Read the meter. Leave the valve shut for half an hour, then read it again. The two readings should match. If the number has gone up, water is passing the meter and going somewhere between it and your closed internal valve, which is your supply pipe.
If the reading does not move with the internal valve shut but your bill is still high, the loss is inside the house, past that valve.
The other signs
Thames Water list reduced flow or pressure at the cold kitchen tap, waterlogged or damp ground in the garden even in dry weather, noisy pipes, and an unusually high metered bill. In London add two more: a patch of pavement or a front path that stays dark when everything around it has dried, and a manhole or basement lightwell that runs clear water long after rain has stopped. Clear, continuously running water in a dry spell is mains water until proven otherwise.
Water in the road
Not yours. Thames Water ask you to report leaks seen in the road or pavement to them. Do that before you pay anybody, because their communication pipe fails in the same places yours does and a leak that surfaces in your garden can still be travelling along the pipe from their side of the valve.
What Thames Water will do on your side, sometimes
Their code of practice describes discretionary help. They will assist customers in their Priority Services Register categories or on their WaterHelp or WaterSure schemes, and will step in where there is a risk to life or to their supply network. Where they do repair, three limits are stated: they will repair the supply pipe up to where it enters your building but will not fix pipework underneath a building, so in a flat that means to the point the pipe enters the main building and no further; they will use trenchless moling where possible; and where they cannot avoid digging on a footpath or driveway they will restore the surface to make it safe but cannot relay block or crazy paving, which you would then arrange and pay for yourself.
Two more from the same document. The supply pipe stays your responsibility throughout, even if Thames Water repaired or replaced it. And their repairs and the associated connections are guaranteed for normal conditions of use for two years, with no guarantee on the condition of the existing pipe either side of the repair.
Tenants and landlords
Thames Water are unambiguous: "If you're a tenant, your landlord is responsible for fixing leaks." Their advice is to tell the landlord or letting agent as soon as possible, in writing, and keep a copy. If you are a tenant reading this because a bill has jumped, that written record is the single most useful thing you can produce later.
Then the clock starts
Once the leak on your property is confirmed, Thames Water's position is that it is your legal responsibility to arrange repair within four weeks, and that if you do not they will carry out and charge you for the repair under section 75 of the Water Industry Act 1991. What that notice can and cannot do is set out separately, along with the statutory seven-day minimum that sits underneath their four-week policy.
When not to call us
Water in the road, the pavement or a neighbouring street: report it to Thames Water, free. A tenant with a leak: your landlord, in writing. A supply pipe that is obviously weeping at a visible joint in an accessible trench: any competent plumber can remake that joint and you do not need detection. Someone on the Priority Services Register, WaterHelp or WaterSure: ask Thames Water about their discretionary assistance first.
Call us when the leak is inside your boundary, nobody can say where on the run it is, and the ground above it is a tiled path, a bay window, a resin drive or a solid floor that somebody has to put back. We trace with acoustic equipment, thermal imaging and tracer gas on a drained line, repair the pipe, and reinstate what was opened. £150 per hour, agreed before we attend, and if we do not find it you do not pay for the time we spent looking.
