Leak detection — London
Leak Detection London - No Find, No Fee
Acoustic, thermal, tracer gas and moisture-mapping leak detection for London homes and businesses, used to pinpoint hidden water leaks without lifting a floor or stripping a wall on spec. We work on a no find, no fee basis where the survey allows it, hand over a clear trace-and-access plan, and provide reports insurers, landlords and agents can act on immediately.
£4.05
Average cost per m³ of water via Thames Water (2025)
20–30%
Of a typical bill that an undetected running leak can add
£1,500+
Typical cost of unrepaired escape-of-water damage to a ceiling below
48hrs
Rough window insurers expect a leak to be found once reported
On this page
What leak detection actually involves in a London property
Leak detection is the process of locating a water leak precisely, without guessing, before any repair work begins. It sits between two problems homeowners commonly get wrong: assuming a leak must be somewhere obvious because a bill has risen or a patch has appeared, and paying a builder to open up walls or floors on a hunch. Proper detection uses acoustic listening equipment, thermal imaging, tracer gas or moisture meters, sometimes in combination, to narrow a suspected leak down to a specific pipe run or joint before anyone reaches for a hammer drill.
London housing stock makes this harder than it sounds. Victorian and Edwardian conversions often have pipework buried under solid screed floors with no accessible void, shared soil stacks running through multiple flats, and plumbing that has been extended and rerouted by successive owners without a plan anyone kept. In purpose-built blocks and ex-local-authority buildings, a leak affecting a downstairs ceiling can just as easily originate from a neighbour's bathroom two floors up, which means detection sometimes needs to establish whose pipework is actually responsible before a repair, or an insurance claim, can proceed.
Getting the detection stage right matters financially as much as practically. Escape-of-water claims are one of the most common categories of home insurance claim in London, and most policies expect the leak to be traced professionally, with a written report, before they will pay out for the repair or the redecoration that follows. A vague "we think it's under the kitchen" is not enough for most insurers or letting agents; a report showing the method used, the reading taken and the specific location found is what actually moves a claim forward.
Scope of work
Leak detection services we provide across London
Every property and every leak is different, so the method is matched to the situation rather than applied by default. These are the core services we carry out.
Acoustic leak detection
Ground microphones and listening rods pick up the distinct sound a pressurised water leak makes as it escapes a pipe, even through concrete, screed or tarmac. This is the primary method for underground supply pipes and leaks beneath solid floors, and it narrows a search area to within a small radius without any digging.
Thermal imaging surveys
A thermal camera reveals temperature differences caused by escaping water, particularly effective for tracing hot water pipe leaks under floors or within walls, and for spotting damp patterns behind plaster before they become visible to the eye. Used alongside moisture readings to avoid false positives from cold bridging.
Tracer gas detection
A safe, non-toxic hydrogen-nitrogen mix is introduced into an empty pipe and escapes through even a pinhole leak, rising to the surface where a handheld sensor detects it. This is often the most accurate method for pinpointing small leaks in underfloor heating loops and buried supply pipes where acoustic methods struggle.
Moisture mapping and damp investigation
Pin and pinless moisture meters map the extent of water ingress across a wall or floor, distinguishing a plumbing leak from penetrating damp, condensation or a defective damp-proof course. This is frequently the first step when a stain appears and the cause is not yet obvious.
Trace and access reporting
Once a leak is located, we provide a trace-and-access report setting out exactly where the leak sits, the likely cause, and the minimum access required for repair — for example a single floorboard rather than an entire ceiling. This report is what most insurance policies require before authorising repair and reinstatement costs.
Insurance claim support
We produce documentation in the format loss adjusters expect, including photographs, readings and a clear narrative of the detection process. Where a claim depends on identifying whether a leak originates from your property or a neighbour's, our report is written to stand up to scrutiny from both insurers.
When to act
Signs you may have a hidden leak
Hidden leaks rarely show themselves as an obvious puddle. These are the signals that most often lead a London homeowner to book a detection survey.
Water bill has risen with no obvious explanation
A steady, unexplained increase in metered water usage, especially over consecutive billing periods, is one of the clearest indicators of a running leak somewhere in the supply pipework. Thames Water and other suppliers can sometimes flag unusual consumption, but by the time a bill arrives the leak may have been running for weeks.
Damp patch, stain or bubbling paint indoors
A ceiling stain, a patch of bubbling paint, or a damp smell in a specific area of a room often marks the point closest to the leak rather than the leak itself, since water tracks along joists and plasterboard before showing through. The visible mark is a starting point for detection, not the answer.
A patch of unusually green or lush grass in the garden
A leaking underground supply pipe or drain often produces a strip of noticeably greener, faster-growing grass along its route, sometimes accompanied by soft or waterlogged ground even in dry weather. This is a classic sign of an external leak worth investigating before it undermines paving or foundations.
You can hear running water with everything turned off
A faint hissing or trickling sound audible when every tap, appliance and outlet in the property is switched off strongly suggests water is escaping somewhere in the system. This is exactly the kind of leak acoustic detection equipment is built to locate precisely.
Water meter keeps moving with everything off
Turning off every appliance and outlet, then checking whether the water meter's leak indicator (often a small triangular or star-shaped dial) is still spinning, is a simple home test that strongly indicates an active leak somewhere between the meter and the property.
Warm patch on the floor or a boiler losing pressure repeatedly
A warm patch on an otherwise cold floor usually points to a leaking underfloor heating pipe or hot water supply run. A central heating system that keeps needing repressurising, with no visible leak at the boiler or radiators, often means the leak is hidden within the pipework itself.
How it works
How a leak detection survey works, step by step
The aim at every stage is to find the leak with the least disruption possible, and to leave you with a report you can actually use, whether that is for a repair, a claim or peace of mind.
01
Initial consultation and history
We start by discussing what has been noticed — a bill increase, a stain, a sound, a boiler pressure issue — and where in the property it has appeared. This history narrows down which detection method is likely to be most effective before the engineer arrives.
02
Visual inspection and isolation testing
On site, we carry out a visual check of accessible pipework, fittings and known problem areas, and isolate sections of the system where possible to establish which zone the leak sits within. This alone sometimes narrows a whole-property problem down to a single circuit.
03
Non-invasive detection survey
Acoustic listening, thermal imaging, tracer gas or moisture mapping is applied, chosen based on the pipe type, construction and suspected leak location. Where useful, more than one method is used to cross-check a single result before it is confirmed.
04
Pinpointing and marking the leak
Once the readings converge on a location, the exact point is marked and measured against fixed reference points in the property, so anyone accessing the area later — us or another contractor — knows precisely where to open up.
05
Trace-and-access report and repair options
You receive a written report describing the method used, the findings, the confirmed or probable location, and the minimum access needed for repair. Where the fix is straightforward we quote it directly; where it needs a specialist trade (flooring, roofing) we say so clearly.
06
Repair, reinstatement and sign-off
Once access is agreed, the repair is carried out, the system is tested for pressure and pushed back into normal use, and any access point is made good or handed to the appropriate trade for reinstatement. A final note confirms the leak has stopped.
Buyer guide
How to choose a London leak detection specialist (and avoid being overcharged)
Leak detection is a field where the customer usually cannot verify the work themselves, which makes it easy for a small number of operators to charge for guesswork dressed up as a survey. These checks help you hire someone who will actually find the leak rather than open up your floor and hope.
Ask exactly what "no find, no fee" covers
No find, no fee is a genuinely useful offer, but the small print varies enormously between companies. Ask whether it applies only to the detection survey itself, or also to any exploratory work carried out, and get the terms in writing before booking. Some operators charge a reduced call-out fee even where nothing is found; ask for that figure upfront.
Ask which detection methods they actually carry
A genuine leak detection specialist should be able to name the equipment they use — acoustic listening devices, thermal camera, tracer gas kit, moisture meters — rather than describing a vague "leak detection service." If a company cannot explain which method suits your specific problem, they are likely to go straight to invasive investigation instead.
Get the report in writing before you commission repair work
A proper detection survey ends with a written report showing the method, readings and located leak point. Do not commission repair or reinstatement work based on a verbal opinion alone, particularly if you intend to claim on insurance, since most insurers require the written trace-and-access report as evidence.
Be wary of anyone recommending immediate invasive work
If a contractor suggests lifting a whole floor or stripping a wall before any non-invasive detection has been attempted, ask why. Non-invasive methods should always be tried first where the pipe construction allows it; invasive investigation is a last resort, not a starting point, and it should be justified in writing.
Check how the claim-relevant reporting is handled
If this is for an insurance claim, ask whether the company routinely deals with loss adjusters and what their report includes — photographs, readings, a clear narrative. A report that satisfies a friend is not automatically one that satisfies an insurer, and a rejected claim over paperwork is a common and avoidable frustration.
Understand the boundary between detection and repair pricing
Detection and repair are typically priced separately: a survey fee to find the leak, then a repair quote once the cause and access point are known. Be suspicious of a single vague all-in figure quoted before any survey has taken place, since it usually means the location is not actually confirmed yet.
2025 pricing
Leak detection costs in London (2025)
These are indicative London price ranges for 2025. Detection and repair are priced separately in most cases, since the repair cost depends entirely on what the survey finds and how accessible it is.
| Job | Detail | Price range (2025) |
|---|---|---|
| Leak detection call-out | Initial visit and assessment | £90 – £150 |
| Acoustic detection survey | Ground microphone and listening equipment | £150 – £300 |
| Thermal imaging survey | Camera survey of suspected area | £180 – £350 |
| Tracer gas survey | Gas injection and detection, per system | £200 – £400 |
| Trace-and-access report | Written report for insurer or landlord | £50 – £120 |
| Straightforward pipe repair | Once leak point is confirmed and accessible | £120 – £350 |
Where a full leak detection survey finds nothing conclusive, the no find, no fee terms agreed at booking apply — always confirm these before the engineer arrives. Repair costs rise significantly where flooring, tiling or plasterwork must be removed and reinstated, and that stage is quoted once the exact access point is known, not before.
Get started
Leak Detection London - No Find, No Fee — get a clear quote
Tell us about the property and the job. A qualified engineer confirms the scope, agrees a price before work starts, and issues the correct certificate on completion. All 33 London boroughs covered.
Common questions
Leak Detection London - No Find, No Fee: frequently asked
What does "no find, no fee" actually mean?
It means that if a full detection survey is carried out and no leak is conclusively located, you are not charged the survey fee. It does not usually cover a reduced call-out charge, and it does not extend to any exploratory or repair work that may already have been agreed separately. Always ask for the specific terms in writing before the survey is booked, since these vary between companies and it is one of the most common sources of dispute afterwards.
Will you need to break into my walls or floors to find the leak?
In most cases, no. Acoustic detection, thermal imaging, tracer gas and moisture mapping are all designed to locate a leak without any invasive work, and these are always tried first where the pipe construction allows. Invasive investigation — lifting a floorboard or opening plaster — is only used once non-invasive methods have narrowed the location, and even then it is usually limited to a small, specific access point rather than a large area.
How long does a leak detection survey take?
A straightforward survey using one detection method typically takes one to two hours on site. More complex cases, particularly where multiple methods are needed or where the leak affects shared pipework in a block of flats, can take longer and may require a second visit once initial findings narrow the search. We give a realistic estimate after hearing the history of the problem, before booking.
Can a leak detection report be used for an insurance claim?
Yes, and for most escape-of-water claims it is required. Insurers generally expect a written report showing the detection method used, the readings taken, and the specific location of the leak before they will authorise repair and reinstatement costs. We format our reports to include this information clearly, and we can liaise directly with a loss adjuster where that speeds up the claim.
The leak seems to be coming from my neighbour's flat — what happens then?
In flats and converted properties, a leak affecting your ceiling can originate from a neighbour's bathroom or kitchen above, and establishing whose pipework is responsible is often the point of the survey. Our report sets out where the leak has been traced to as precisely as possible, which is usually the evidence needed to determine responsibility between the two insurers or, in a managed block, the freeholder or managing agent.
Is tracer gas safe to use in an occupied home?
Yes. The gas mixture used is a safe blend of hydrogen and nitrogen, non-toxic and non-flammable at the concentrations used for leak detection. It is introduced into an isolated, empty section of pipework, not into the water supply itself, and dissipates quickly once the survey is complete. It is one of the more precise methods available for small leaks in underfloor heating and buried pipework.
What should I do while I am waiting for a leak detection appointment?
If you can safely isolate the affected pipe or the whole water supply without causing further inconvenience, doing so can limit ongoing damage and water loss. Avoid attempting to dig up or open into any area yourself, since this can obscure the very evidence a non-invasive survey relies on. Photograph any visible staining or damage as it develops, and keep a note of when it was first noticed, since this history is useful during the consultation.