Water Company Leak or Your Plumber’s Job?

Why the boundary stop tap is the dividing line

Water reaches your home through the main under the road, a short branch pipe the water company owns, and then your own supply pipe. The handover happens at the boundary stop tap, a small valve under a cover in the pavement or just inside your front garden. Upstream of it, the water company repairs everything. Downstream of it, the property owner does, and that includes the buried pipe under the garden, the internal stopcock, tanks, cylinders, taps and appliances.

Most of the confusion comes from the fact that the problem rarely shows up where the fault is. A leak on your own supply pipe can surface in the pavement. A fault on the main can look like a problem with your boiler or your taps. So the useful question is not where the water appears, but which side of that stop tap the cause sits on. Our guide to who owns the water pipe to your house covers flats, shared supplies and houses with no visible stop tap.

Who to call first, symptom by symptom

Use this as a starting point. Where it says “check first”, the three tests in the next section will usually settle it in a quarter of an hour.

• Clear water running out of the road or the far side of the pavement: the water company
• Water pooling in your front garden or under your path: probably your supply pipe, so a plumber, but check first
• Water leaking indoors from a pipe, joint, tank, cylinder or appliance: a plumber, every time
• No water at all, and your neighbours have none either: the water company
• No water at all, but the houses either side are fine: check first, as it is often a closed or failed valve on your side
• Weak flow at every tap, and the street is the same: the water company
• Weak flow at one tap or only on hot: a plumber
• Brown or cloudy cold water from the kitchen tap after work in the road: the water company
• Sewage smell or a blockage shared with neighbours: the water company’s sewerage team
• Blockage in a drain that only serves your home, inside your boundary: yours, so a plumber or drainage contractor

If a leak is near electrics or a light fitting, switch off at the consumer unit only if you can reach it with dry hands while standing somewhere dry. If the consumer unit itself is wet, keep away from it and do not use the switches below the leak. If you smell gas anywhere, open windows, turn the gas off at the meter if it is safe to reach, avoid switches, and call the National Gas Emergency Service on 0800 111 999 from outside.

Three checks that tell you whose problem it is

None of these needs tools beyond a torch, and none involves opening anything that holds water under pressure.

First, ask a neighbour. Knock on the door either side and ask whether their water is normal. If two or three houses have the same problem, it is almost certainly on the network, and your water company’s website will usually already show a live incident for your postcode. If only your house is affected, the cause is almost always on your side. No water in the house when the neighbours have water walks through that case.

Second, try the internal stopcock. Find it, usually under the kitchen sink or, if it is not under the sink, where the pipe comes up through the floor, and turn it fully clockwise. Then look at the leak. If the dripping or spraying stops within a few minutes, the fault is on your indoor plumbing, which is a plumber’s job. If water keeps coming at full strength with the stopcock closed, the leak is upstream of it: on your buried supply pipe, at the boundary stop tap, or on the water company’s side. One exception: a leak fed by a loft tank, a hot water cylinder or the heating system can keep running for a while after the stopcock is shut, because it is draining stored water, so a slowly easing leak indoors is still yours.

Third, if your meter is outside in the pavement, use it. With the internal stopcock still closed and nothing drawing water, lift the meter cover and watch the dial for a couple of minutes. A dial that keeps turning means water is passing the meter and escaping somewhere before your stopcock, which points to your supply pipe. A still dial with water still surfacing outside points to the network side, or to the short stretch of pipe before the meter. Reading the dial properly is covered in water meter running with no taps on.

Open the stopcock again slowly once you have your answer, unless water is coming into the house.

What the water company will and will not do

On their side of the boundary, the water company finds the fault, digs, repairs and reinstates the surface at no charge to you. If you are not sure whose leak it is, report it anyway. They will usually send someone to look, and if it turns out to be on your supply pipe they will tell you, which gives you something to show a plumber or an insurer.

Pressure has a reference level. Water companies in England and Wales work to a reference level of service of 10 metres head (about 1 bar) on your side of the boundary stop tap with a flow of 9 litres a minute, which is enough to fill a 4.5-litre container in about 30 seconds. If your whole house falls short of that and the street does too, it is theirs to investigate. If the supply is fine at the boundary but weak at your taps, the restriction is in your pipework, often a part-closed stopcock, a narrow old lead pipe or a failing pressure reducing valve.

Drains changed hands in England and Wales on 1 October 2011. Since then, sewers and lateral drains that serve more than one property, or that run outside your boundary, have been the water company’s responsibility. A drain that serves only your home and sits within your boundary is still yours. The Thames Water blocked drain guide explains how to tell the difference at the inspection chamber.

What they will not do is touch anything inside your home. They will not repair a leaking stopcock, a split pipe under the floor, a dripping tank overflow or a failed cylinder valve, and a leak on your supply pipe is normally yours to arrange and pay for. Some water companies offer help with supply pipe repairs from time to time, so it is worth asking when you report it. On a metered supply, ask them about a leak allowance once a leak on your side has been repaired, as it can take the lost water off your bill.

When it cannot wait for the water company

Reporting a leak on the network gets it into a queue, and a leak that is not affecting anyone’s supply or safety may sit there for days. That is fine when water is running into a gutter. It is not fine when water is getting into your building.

Call a plumber straight away, whoever turns out to own the pipe, if water is coming through a ceiling or up through a floor, if it is anywhere near wiring, if a basement or cellar is flooding, or if you cannot shut it off because the stopcock will not turn. The priority is to stop the water and make the building safe. Ownership can be argued over in daylight.

An engineer can close the boundary stop tap with a proper stop tap key, which most households do not own, and can fit a temporary isolation or repair so you are not left without water all night. If the fault then proves to be on the water company’s side, you report it with the engineer’s findings, and they carry out the permanent repair.

Do not dig down to a buried pipe yourself to find a leak. Supply pipes often run near gas and electricity cables, and a pipe under pressure can wash out the ground around it faster than you expect.

What a plumber does on a “whose leak is it” call

The visit usually follows the same order. The engineer isolates the supply, confirms whether the internal stopcock holds, reads the meter with everything closed, and checks the pressure at the kitchen tap with a gauge. That tells them whether the fault is inside, on the buried supply pipe, or beyond your boundary.

Inside, most faults are fixed on the first visit: a failed joint, a split pipe, a stopcock that weeps from its gland, or a tank valve stuck open. On the supply pipe, a single failed joint can often be cut out and replaced with a coupling rated for burial. An old lead or galvanised supply pipe is usually better replaced in blue MDPE plastic, which is a bigger job priced on length, depth and what surface has to come up. A single buried joint repair is a much smaller job than a full supply pipe replacement.

With us, the visit is the £60 call-out at any hour, and the repair price is agreed with you on site before any work starts. If the engineer finds the fault is on the water company’s side, you will be told so, with what was found, so you can report it without paying for a repair that is not yours. See water leak repair for a leak on your side, or our no-water emergency call-out if the supply has stopped altogether. Full charges are on the pricing page.