Leak detection for homes across Wales

Leak detection across Wales tracks down water escaping unseen from a home's pipes, its heating circuit or the buried pipe that brings its supply in, and pins it to one spot without breaking into a wall or floor first. Cambrian Leak Detection does this work across mainland Wales, from Cardiff to the north coast.

What does leak detection cover in a Welsh home?

Leak detection in a Welsh home covers four kinds of hidden leak: the water pipes inside the house, the central heating circuit, the underground supply pipe that brings water in, and leaks an insurer pays to have traced.

Water pipe leak detection

Hot and cold pipework runs out of sight under floors, inside walls and above ceilings, and a leak can start at any joint or fitting along it, or on an appliance such as a washing machine.

Where it leaks: Water pipes run out of sight under floors, inside walls and above ceilings, and a leak can start at a joint or a fitting, or on an appliance such as a washing machine.
Signs you may notice: Look for brown stains or damp patches on a ceiling or wall, a musty smell or mould, floorboards that warp, the sound of water running with all the taps closed, and weaker flow from the taps.
Methods that suit it: Pressure testing confirms the loss, thermal imaging follows hot pipes, acoustic listening hears water escaping under pressure, tracer gas finds leaks that make no sound, and moisture mapping shows how far the water has spread.
Who repairs it in Wales: Both Welsh water companies' rules leave the pipework and fittings inside a home for the owner to repair, and if the home is rented in Wales, it is the landlord who has to keep its water installations in repair and proper working order.

Central heating leak detection

When the boiler gauge keeps falling, the sealed circuit behind it is losing water, most often at a radiator valve, though the leak can also sit in pipework under a floor or inside the boiler.

Where it leaks: A sealed heating circuit most often leaks at radiator valves and other system components, and it can also leak from pipework hidden in floors and walls, from underfloor heating loops and from inside the boiler.
Signs you may notice: Signs include a boiler gauge that keeps dropping below 1 bar, top-ups needed once a month or more, and damp patches or rust marks around radiators; a dripping discharge pipe outside can instead mean a faulty pressure relief valve.
Methods that suit it: Pressure testing shows whether the circuit holds and, on underfloor heating, which loop leaks; thermal imaging finds the warm patch that escaping hot water makes; tracer gas and acoustic listening help where heat alone does not show the leak.
Who repairs it in Wales: Repairing pipework inside the home falls to the owner, and in a rented home in Wales the landlord must keep heating and hot water installations in repair and proper working order; Vaillant advises getting a Gas Safe Registered engineer to inspect a boiler that may be leaking.

Underground leak detection on the supply pipe

Buried between the water company's part and the house, the supply pipe often runs under a drive or garden, and Welsh Water says it won't always be obvious when something is wrong with it.

Where it leaks: Buried between the water company's part and the house, the supply pipe often passes under a drive, path or garden, and it can be long enough to cross a neighbour's land.
Signs you may notice: Signs include lush or greener grass, damp patches on the ground or sunken paving, a big drop in water pressure, a hissing noise near the internal stop tap and, where a meter is fitted, a bill that rises with no extra use.
Methods that suit it: Loss is confirmed with a meter test or a pressure test; then a ground microphone listens for water escaping from the pressurised pipe, or tracer gas works up through grass, block paving, tarmac or concrete to a detector above.
Who repairs it in Wales: Both Welsh Water's and Hafren Dyfrdwy's rules leave the supply pipe to the owner, share the responsibility where one pipe serves several homes, and come with limited help on each company's own terms.

Trace and access leak detection

Where a home policy includes trace and access, the insurer pays for the hidden leak to be found and reached, and its position, the access needed and photographs are recorded for the claim.

Where it leaks: Trace and access is for escape of water, such as a leaking or burst pipe hidden under a floor, inside a wall or above a ceiling, and Welsh Water says some policies also cover leaks on the supply pipe outside.
Signs you may notice: The usual starting point is water damage with no visible source, such as a damp patch on a ceiling whose cause cannot be found.
Methods that suit it: Insurer and comparison guides name thermal imaging, acoustic methods and tracer gas among the ways a trace and access search finds a leak.
Who repairs it in Wales: The policy decides what trace and access pays, the repair of the leaking pipe falls outside it, and in a rented home in Wales the landlord deals with leaks on the water, heating and hot water installations.

What gives away a water leak you cannot see?

A water leak you cannot see gives itself away through the signs Welsh Water, insurers and boiler makers list: a damp patch or stain, a boiler that keeps losing pressure, a big drop in water pressure, a hissing noise near the internal stop tap, ground that stays damp, and an unexplained change on a metered bill.

Signs like these are easy to live with for a while. Hafren Dyfrdwy asks owners to fix leaks promptly to avoid damage and high bills, so a stain or a bill that turns up out of nowhere deserves a closer look. The signs below are grouped by where each one shows, with the organisation that lists it.

Ceilings and walls: Brown staining or damp patches, which Aviva says are usually the first thing a household sees of a leak, and a musty smell or mould, which it links to a possible hidden leak in the pipework.
Floors: Warped floorboards, on Ageas's list, and water stains on a floor, on Vaillant's, can point to a leak at or under it.
The boiler: A pressure gauge that keeps dropping: Vaillant counts a leak on the heating circuit among the commonest causes, and Ideal says repeated top-ups may mean a small leak.
Taps and the stop tap: Water you can hear running with every tap off, which Aviva says could point to a leak, weaker flow at the taps, and the hissing noise near the internal stop tap that Welsh Water lists for the supply pipe.
Outside: Lush vegetation and damp patches on the ground, from Welsh Water's list, and the wet patches, greener grass and sunken paving that Hafren Dyfrdwy names.
The water bill: An unusually high metered bill, which Welsh Water's code of practice says may indicate a leak.

Where a mark appears does not always say where the water came from. In one case the Financial Ombudsman Service decided, water staining a kitchen ceiling came from a leaking shower supply pipe in the bathroom upstairs.

Only a metered home will see a leak on its bill. Around half of Welsh Water's customers have a meter, and Hafren Dyfrdwy's customer research put the share at almost 6 in 10 homes in its region. But even where the bill has not moved, water could still be escaping: an unmetered Welsh Water customer pays a set annual charge that a leak does not change.

Which methods pinpoint a leak without guesswork?

The methods that pinpoint a hidden leak are acoustic listening, thermal imaging, tracer gas, pressure testing and moisture mapping, and each reads its own sign of escaping water: sound, a temperature difference, rising hydrogen, falling pressure or damp.

Which method fits depends on the pipe (whether it carries hot water, stays under pressure or lies buried under a drive) and on the leak itself. Where one method has nothing to work with, another takes over: for a leak too quiet to hear, Sewerin recommends tracer gas. The table sets each method beside what it detects, the leaks it suits and its limit.

Method	What it detects	Leaks it suits	Its limit
Acoustic listening	The sound a pressurised pipe makes where water is leaving it.	Any pipe kept under mains or system pressure: buried supply pipes and house service connections, plus water, heating and sanitary pipework indoors.	A quiet leak, or a pipe with no pressure in it, gives nothing to hear; for those, Sewerin recommends tracer gas.
Thermal imaging	Temperature differences on a surface.	Underfloor heating, radiator circuits and hot water pipes, including runs beneath tiled or concrete floors, and the extent of damp across a wall or ceiling.	The camera reads surfaces only, so a pipe or leak behind them shows only where it changes the surface temperature, and a cool patch may turn out to be a draught; other checks confirm what it suggests.
Tracer gas	Hydrogen coming up through the surface from the leak.	Buried supply pipes, heating and underfloor heating systems, plastic pipes, and leaks that are small, hard to find or make no sound; the gas comes up through grass, block paving, tarmac and concrete.	The gas can take very different times to reach the surface, depending on what lies above the pipe.
Pressure testing	Pressure draining away from a section that has been sealed and tested.	Proving that a suspected leak is real without breaking into a wall or floor first, then narrowing it down: sealed heating circuits, water pipework, and underfloor heating loop by loop.	Plastic pipe expands slightly when pressurised and any trapped air must be let out first, so a gauge that drops is not, on its own, proof of a leak.
Moisture mapping	Which spots on a wall, floor or ceiling read wetter than the rest.	Walls, floors and ceilings that leaking water has soaked into, even where tiles, vinyl or another covering hides the surface.	Readings are comparisons between spots: meters calibrated for timber cannot be relied on as measurements in plaster, brick or stone, and surface salts or nearby metal can inflate them.

Tracer gas is a mix of 95% nitrogen and 5% hydrogen, and Sewerin and INFICON both say it will not burn, is not poisonous and does not corrode.

What does a visit involve, from confirming the leak to recording where it is?

A visit involves confirming that water is being lost, narrowing the search to the pipe or circuit losing it, pinpointing the leak by whichever methods fit that pipe, and recording where it is for the owner, the plumber or the insurer.

Confirm that water is being lost
The first job is proving the loss before anyone breaks into a wall or floor. A meter dial that still moves once all the water is off points to a leak, and so does a sealed section that loses its test pressure after trapped air and the slight give of plastic pipe are allowed for.
Isolate the system losing it
Next the search narrows to one system, or one part of it, which a pressure test closes off and tests on its own; underfloor heating can be tested loop by loop.
Locate the leak on that pipe
Then the leak is pinned down with whichever methods suit the pipe: listening along it under pressure for the point where the sound peaks, following the warm patch a heated pipe leaves, or passing a hydrogen detector over the surface to find its highest reading.
Record where the leak is
The search ends in a write-up of where the leak sits and the access needed to reach it, which, in Confused.com's account, is what trace and access specialists send to the insurer. Insurers and comparison sites advise keeping photographs, invoices and reports as well.

Not every leak can be found. Welsh Water says there may be times it cannot locate one, and Fluke notes that a thermal camera points to a probable zone without always settling the question, so some breaking into a wall or floor may still be needed.

Where does your responsibility for pipes start in Wales?

Your responsibility for pipes in Wales normally starts at the boundary of the street the main is laid in if Welsh Water supplies your water, and just after the external stop tap if Hafren Dyfrdwy does; every pipe from that point into the house, and every pipe inside it, belongs to the owner.

Welsh Water's part stops at the street boundary and Hafren Dyfrdwy's at its external stop tap, so the owner's share of the pipe depends on which company supplies the home.

Where Welsh Water supplies the home, its code of practice makes it normally responsible for the main, any stop tap set in the road or pavement, and the communication pipe, the short stretch from the main to the street boundary. Past that boundary the owner takes over: the private supply pipe up to the internal stop tap, then every pipe and fitting indoors. Even so, Welsh Water says it “will offer a free repair where possible” on the private supply pipe, an offer its code says it may make, subject to certain conditions.

Hafren Dyfrdwy draws its line in a different place. Its responsibility runs up to and including its controlling external stop tap, normally at the property boundary, although it says this isn't always the case, and by law the owner maintains the private pipes inside and outside the property. If Hafren Dyfrdwy has written to a customer about a leak, it can offer domestic customers a free of charge repair, subject to conditions; leaks covered by household insurance are not part of that scheme.

Living near the edge of Hafren Dyfrdwy's region? The company says it can be hard to tell whether a property there is inside it, and asks people to contact it through its supply area page. Where one pipe serves several homes, both companies share the responsibility among them, and the supply pipe page sets out who owns the underground supply pipe when it serves more than one property or crosses a neighbour's land.

If you rent your home in Wales, you are a contract-holder. The Renting Homes (Wales) Act 2016 replaced tenancies with occupation contracts. For a secure contract, a periodic standard contract or a fixed term standard contract made for less than seven years, section 92 makes the landlord keep the service installations, which include those for the supply of water, space heating and heating water, in repair and proper working order. Welsh Water suggests speaking to the landlord straight away, since the repair may fall to them to arrange.

When does an insurer cover the cost of finding a leak?

An insurer covers the cost of finding a leak when the home policy includes trace and access cover, and then only the costs directly related to finding it, not the repair of the leaking pipe.

In MoneySuperMarket's words, insurers will only pay for costs “directly related to finding the leak”. Mending the leak itself sits outside trace and access, according to MoneySuperMarket and Confused.com. Financial Ombudsman Service decision DRN-5382026 points the same way: in that case the cover was found not to pay for repairing the leaking pipe.

Whether the cover is there at all comes down to the policy wording. Confused.com says trace and access is usually part of buildings insurance but that every policy varies, and that it applies to escape of water, such as a burst pipe, and does not reach water coming in from outside. Admiral advises checking the policy documents for the cover and its limits.

Remember to speak to the insurer before any work starts. Ageas needs to have agreed the work first, and Admiral will usually ask the policyholder to bring in a professional, whose bill may have to be paid up front and claimed back later. Cambrian Leak Detection's guide to trace and access cover for an escape of water claim sets out what the search records for the insurer and how the Welsh rules on supply pipes and renting affect who claims.

Where does the Welsh coverage stop?

The Welsh coverage of Cambrian Leak Detection stops at the edge of 173 mainland postcode districts in the CF, SA, NP, LL, CH, SY and LD areas, from Cardiff, Swansea and Newport to Wrexham, Aberystwyth and the north coast; no island is covered.

Every point on this map stands for one covered postcode district, placed at its approximate centre, and labels name the five places with pages of their own. Contains OS data © Crown copyright and database right 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Source: Office for National Statistics licensed under the Open Government Licence v.3.0.

Cardiff: In the Cardiff council area, 20.2% of households lived in purpose-built flats in 2021 and 24.3% rented privately, the highest shares of both among the five places with their own pages, and the page on leak detection in Cardiff covers who deals with a leak between flats or in a rented home.
Swansea: Of the five places, the Swansea council area has the biggest share of dwellings built before 1919, 26.4% at 31 March 2026, so the Swansea leak detection page looks at why the age of a home matters for its pipes.
Newport: Terraced houses held 31.1% of Newport council area households in 2021, more than in any of the other four places, and leak detection for Newport, south Wales covers what happens when one supply pipe serves a terrace.
Wrexham: Hafren Dyfrdwy supplies water to its customers in Wrexham, while Welsh Water provides the wastewater services there, and the page on Wrexham leak detection sets out Hafren Dyfrdwy's supply pipe rules.
Bridgend: Owner-occupiers, the only customers Welsh Water's Leak Support Scheme serves, made up 70.5% of Bridgend council area households in 2021, the highest share of the five, and the page on leak detection in Bridgend explains who the scheme is for.

Beyond those five, the coverage takes in the larger towns of Llanelli, Neath, Barry, Pontypridd and Caerphilly, and the towns page lists every covered town and postcode district with its post town. Anglesey, with Holy Island, is left out. The about page explains what Cambrian Leak Detection does and why the business is called Cambrian.

Water escaping in the street or the pavement is on the water company's pipe, so report it to the company: on Welsh Water's Report an issue page, after checking its Network Leakage page to see whether it already knows about the leak, or on Hafren Dyfrdwy's Report a problem page, after checking the latest updates for your area.