Does a leak on my own pipe count towards the water company’s leakage figure?

Yes. Thames Water define leakage as all the water not making its way to customers and state that water is also lost on customers’ pipes and through unmeasured consumption. It counts against their performance even though their report states that customer leaks are not on their network and are the customer’s responsibility to fix.

Is a leaking toilet counted as leakage?

Not in the industry sense. It is past your meter, so on a metered supply it is recorded as consumption — water you used. Thames Water nonetheless cost it at up to £161.33 a year for a trickle, £483.99 for rippling water and £6,453.20 for continuous flow, so it is a leak in every way that matters to your bill.

Why is the damp patch not above the leak?

Because water travels. It runs along a joist, a duct, a pipe sleeve or a layer of made ground until it finds somewhere to emerge. Thames Water make the network version of the same point, noting that visible leaks reaching the surface are larger but do not normally lose as much water as the hidden ones.

What does a water company mean when it says a leak is fixed?

That the flow has stopped and the highway has been made safe. Their published process is locate, assess, plan, repair, with priority set by the volume lost, the effect on supply, complexity and location. Nothing in that definition covers a floor, a screed or a ceiling inside a property.

What has to be true for a leak to qualify for an allowance?

Thames Water require the repair within four weeks of them notifying you or the leak being identified, confirmation of the repair by a plumber’s details and invoice or a Thames Water job number, that the leak was not fixed under section 75 of the Water Industry Act, and a claim within three months of the repair date.

What the Water Industry Counts as a Leak, and What You Count

Thames Water define leakage as "all the water not making its way to our customers", a volume measured in megalitres per day that includes losses on customers’ own pipes. You define a leak as a place that needs opening up. A leaking toilet fits neither definition properly, which is why it can cost thousands a year and appear on nobody’s report.

Leak Fix LondonLast updated 19 September 2026

The Leak Fix London van outside a London property

Their definition

Thames Water's leakage performance report opens with it: "Leakage is lost water — that's all the water not making its way to our customers. Water leaks from ageing pipes or pipes that have been damaged on our network. Water is also lost on our customers' pipes and through unmeasured consumption."

Three things follow from that sentence, and none of them are obvious.

First, leakage is a volume, not an event. It is measured in megalitres per day, and the report gives the scale: one megalitre is around 12,500 baths, or 40% of an Olympic swimming pool. A regulatory target is a number of megalitres, averaged over three years.

Second, the losses on your side of the boundary are in their figure. A pinhole in your supply pipe is water not reaching a customer, so it counts against the company's leakage performance even though the company will not fix it and the report says so directly: "Customer leaks aren't on our network, and it is the customers responsibility to fix these." They are measured by it and not responsible for it, which explains a good deal about the tone of the letters.

Third, "unmeasured consumption" is in there too. Water used at properties without a meter is estimated rather than counted, and the error in that estimate lands in the leakage figure. Which means an unmetered house with a leaking toilet is, statistically, part of the national leakage problem, and a metered house with the identical toilet is not.

Your definition

Nobody has ever rung us about megalitres. A leak, to the person who has one, is a place: a stain spreading on a ceiling, a warm patch underfoot, a gauge that will not hold, a smell in a cupboard, a bill that doubled. The unit is not volume. It is square metres of floor that have to come up.

That is the whole difference, and it explains why a water company's extraordinary detection capability is of so little use to you personally. They are optimising a total. You need a coordinate.

The losses that are nobody's leakage and your biggest bill

Take a leaking toilet, which is the single most common continuous loss in a London home. It is past your meter, so on a metered supply it is measured consumption. To the industry, you used that water. To you, it is a leak, and Thames Water price it on their own identifying leaks page: a small trickle wastes up to 200 litres a day and costs an extra £161.33 a year, rippling water around 600 litres a day and £483.99 a year, and water flowing constantly up to 8,000 litres a day and £6,453.20 a year. They also put an average leaky loo at around 400 litres a day, "equal to five full bathtubs".

There is no report anywhere in which those losses appear as leakage. They appear as you using water. If you are unmetered they appear as nothing at all, which is why unmetered houses can run a leaking cistern for a decade.

The same asymmetry applies to a heating system that needs topping up every week. No meter records it, because it is filled from the mains through a loop that opens for thirty seconds. It is a loss, it is doing damage somewhere under a floor, and it is invisible to every measuring system in the chain except the pressure gauge on the boiler. The boiler pressure hub is the diagnosis for that one.

Visible, reported, and actually significant

One more line from the leakage report deserves to be better known: "Over 95% of leaks are never seen by our customers. They're often small, underground, and hard to find. Visible leaks — the ones that do reach the surface — are larger, but they don't normally lose as much water."

Read that twice. Visibility and volume are not correlated. The leak you can see is the one that found a path to the surface, which usually means it is shallow, recent or fast. The leaks that move real volume are the ones that found somewhere to go: a drain run, a soakaway, made ground, a Victorian rubble foundation, the gravel bed the pipe was laid in.

The domestic version of the same rule is the one we spend most of our time explaining. The wet patch is where the water arrived, not where it left. On a first-floor bathroom the stain on the ceiling below is frequently two metres from the failure, because water tracks along a joist before it finds a gap. Chasing the stain is how ceilings get opened twice.

What "fixed" counts as

Thames Water publish their own process: locate, assess, plan, repair. Assessment prioritises "based on the amount of water being lost, the effect on customers' water supply, the complexity, and the location". They talk about improving leak cycle time and reducing the average age of leaks, and they resurface the road afterwards.

That is a completely rational definition of fixed for an operator of a network: the flow has stopped and the highway is safe. It is not the definition that applies in a house, where "fixed" means the pipe holds pressure, the screed is dry, the floor is back down, the ceiling is painted and the room is usable. Two different jobs share one word, and the second one is the expensive half.

What counts for an allowance

There is a fourth definition, which is the one that decides whether you get any money back. Thames Water's conditions are that the leak is repaired within four weeks of them first notifying you or of the leak being identified, that the repair can be confirmed with a plumber's details and invoice or a Thames Water job number, that the leak was not fixed under section 75 of the Water Industry Act, and that the claim is made within three months of the repair date. The evidence pack an allowance needs goes through each one.

Note what that definition rewards. Not the size of the leak, not the damage, not how unfair it was. Speed, and paperwork.

What counts for us

A leak is located when there is a mark on the ground or the floor and a depth, and someone is prepared to put the hole there. Everything short of that is a hypothesis. The methods that get from hypothesis to coordinate are acoustic correlation on pressurised metal, tracer gas on a drained line where plastic pipe defeats acoustic, thermal imaging where the run passes under a floor, moisture mapping to bound the wet area, and pressure testing to confirm the loss is real and to size it before anybody lifts anything.

The deliverable is the position. The floor comes up once.

When not to call us

If the loss is a dripping tap, a running overflow or a leaky loo, that is a washer, a float valve or a flush valve, and any competent plumber will sort it for a fraction of detection rates. Thames Water publish a paper test for the loo: dry the back of the pan, place a dry sheet of toilet paper there, leave it three hours without flushing, and if it is wet or torn you have your answer. If the water is in the road, report it. If you rent, tell your landlord in writing.

Call us when a loss is confirmed, invisible, and under something that will have to be opened. £150 per hour agreed before we attend, no find no fee on the detection, and the making good is ours as well as the repair.

Frequently asked

Does a leak on my own pipe count towards the water company’s leakage figure?: Yes. Thames Water define leakage as all the water not making its way to customers and state that water is also lost on customers’ pipes and through unmeasured consumption. It counts against their performance even though their report states that customer leaks are not on their network and are the customer’s responsibility to fix.
Is a leaking toilet counted as leakage?: Not in the industry sense. It is past your meter, so on a metered supply it is recorded as consumption — water you used. Thames Water nonetheless cost it at up to £161.33 a year for a trickle, £483.99 for rippling water and £6,453.20 for continuous flow, so it is a leak in every way that matters to your bill.
Why is the damp patch not above the leak?: Because water travels. It runs along a joist, a duct, a pipe sleeve or a layer of made ground until it finds somewhere to emerge. Thames Water make the network version of the same point, noting that visible leaks reaching the surface are larger but do not normally lose as much water as the hidden ones.
What does a water company mean when it says a leak is fixed?: That the flow has stopped and the highway has been made safe. Their published process is locate, assess, plan, repair, with priority set by the volume lost, the effect on supply, complexity and location. Nothing in that definition covers a floor, a screed or a ceiling inside a property.
What has to be true for a leak to qualify for an allowance?: Thames Water require the repair within four weeks of them notifying you or the leak being identified, confirmation of the repair by a plumber’s details and invoice or a Thames Water job number, that the leak was not fixed under section 75 of the Water Industry Act, and a claim within three months of the repair date.

Sources

No find, no fee · £150 per hour. The rate is fixed before we attend and does not rise for a difficult property, an awkward access or an evening visit. The total depends on how long the job takes; the rate cannot change.