Leak Detection London — Find the Leak Without the Damage
Hidden leaks under floors, behind walls or below concrete can go undetected for months — causing structural damage, mould and inflated water bills. Our specialist engineers use thermal imaging cameras, acoustic listening equipment and tracer gas to pinpoint leaks precisely before opening anything up.
Gas Safe Registered
All gas engineers Gas Safe ID 123456
24/7 Emergency
Plumbers available every day of the year
No Call-Out Fee Over 2 Hours
£60 waived on jobs exceeding 2 hours
30-Day Workmanship Guarantee
All repairs guaranteed in writing
Non-Invasive
Detection Method
3-Tech
Thermal·Acoustic·Gas
24–48hr
Survey Booking
100%
Written Reports
All 33
Boroughs
What We Cover
Thermal Imaging Surveys
Infrared cameras detect temperature anomalies caused by pipe leaks under floors or behind walls. Non-invasive, no drilling — the camera shows exactly where moisture is present, accurate to within a few centimetres.
Acoustic Leak Detection
Electronic listening equipment picks up the sound of water escaping pressurised pipes. Effective for buried mains, pipes under concrete slabs, tarmac driveways and garden paths where thermal imaging can't reach.
Tracer Gas Detection
A harmless mix of hydrogen and nitrogen is pumped into the pipe. The gas escapes at the leak point and is detected at surface level with a sensitive probe — accurate to within centimetres even through concrete.
Underfloor Heating Leak Location
Underfloor heating pipe leaks cause damp patches and uneven floor temperatures. We locate the exact loop failure without lifting the whole floor — saving thousands in disruption costs.
Water Main Leak Location
If your water bill has spiked or you have unexplained damp patches, we can survey the incoming supply main from the meter to your stopcock to find any loss of pressure in the buried section.
Swimming Pool & Specialist Pipe Leaks
We locate leaks in swimming pool pipework, buried supply pipes and complex systems — services requiring specialist equipment most plumbers don't carry. Written report accepted by pool insurers.
Pricing Guide
Leak detection is priced by survey type and property size. All surveys include a written report with photos, moisture readings, and recommended repair method — accepted by most insurers for escape-of-water claims.
| Job type | Typical cost | Notes |
|---|---|---|
| Thermal imaging survey (up to 3 rooms) | £180–£280 | Includes written report with annotated photos. Same-day results. |
| Acoustic leak detection (buried or external pipe) | £220–£380 | Suitable for mains pipes, driveways, garden paths. Report included. |
| Tracer gas survey (complex or confirmed leak) | £280–£480 | Most accurate method. Combines well with acoustic for buried leaks. |
| Combined thermal + acoustic (larger properties) | £380–£580 | Covers both pipe-borne and surface moisture simultaneously. |
| Emergency callout + detection (same day) | £95 callout + survey fee | Callout waived if job exceeds 2 hours total. |
All prices include VAT. Survey price is fixed before we start — no hidden extras if the leak takes longer to locate than expected.
Leak Detection Methods — Choosing the Right Survey
| Method | Best For | Limitations | Cost |
|---|---|---|---|
| Thermal imaging | Leaks in walls, floors, ceilings — heated or cooled water visible as temperature differential | Works best when temperature difference exists (not effective for cold water pipes at room temp in a warm room) | £180–£280 (up to 3 rooms) |
| Acoustic detection | Buried mains, pipes under driveways/paths, pressurised pipes where water escape creates sound | Less effective in noisy environments; deeper burial reduces signal quality | £220–£380 |
| Tracer gas (H2/N2) | Most accurate — pipes under concrete, tarmac, deep in screed; confirms thermal/acoustic findings | Pipe must be isolated and depressurised to introduce gas; slightly longer setup | £280–£480 |
| Moisture meter survey | Mapping damp extent after a leak; confirming drying progress; establishing leak boundary | Identifies moisture, not the pipe — needs combining with active detection method | £95–£150 |
| Endoscope camera | Checking inside walls and voids without opening up; confirming leak location after other detection | Limited reach and can't pass through bends; not suitable for buried pipes | £120–£200 |
London-Specific Facts
100+ years
Age of water mains in many parts of central London — Islington, Hackney, Kensington — where original Victorian iron mains are still in service and developing slow pinhole leaks.
60–80%
Cost reduction achieved by locating a leak precisely before any opening-up, compared to exploratory cutting without prior detection. On a leak under 30m² of flooring, the saving is typically £2,000–£5,000.
London Clay
Geological formation underlying most of central and inner London. Seasonal moisture variation causes significant shrink-swell movement in clay soil, stressing buried pipework and underground joints.
15–30%
Proportion of London escape-of-water insurance claims where the source of the leak is in a different flat to where the damage appears — making non-invasive detection essential before opening up the wrong property.
24–48hrs
Typical booking lead time for a non-emergency leak detection survey in London. Emergency same-day surveys are available with a 30–60 minute response across most London boroughs.
How It Works
Call and describe the symptom
Tell us what you're seeing — damp patch, high water bill, sound of running water, floor warmth. We'll advise which detection method best suits your situation and book an engineer.
Non-invasive survey on site
The engineer arrives with thermal camera, acoustic equipment or tracer gas kit (depending on the survey type booked). The property is surveyed room by room or pipe by pipe without any opening-up.
Pinpoint location confirmed
We mark the precise leak location on your floor or wall. The written report includes photos, moisture meter readings, the exact location reference and our recommended repair method.
Repair option on the same visit
For accessible leaks, we can carry out the repair immediately. For leaks under concrete, we quote for the most appropriate access method and can return on a confirmed date.
Why Hidden Leaks Are Particularly Common in London Properties
London's housing stock is older than almost any other major city. Many homes in Islington, Hackney, Southwark and Kensington still have lead or iron water mains — some dating from the Victorian era — that have corroded from the inside out over 100+ years. These pipes don't fail dramatically; they develop pin-hole leaks that lose a few litres per day, enough to cause significant damp and mould over months without ever causing visible flooding.
The London Clay geology beneath the city also causes significant ground movement through seasonal shrinkage and swelling. Buried plastic pipes can be stressed by this movement, and older lead or iron mains that span clay-to-gravel boundaries can develop cracks at the transition point. These leaks are deep enough that no surface moisture appears — the water just migrates through the soil and evaporates.
Purpose-built flats present a separate category of hidden leak. Communal hot water risers, individual flat supply pipes running under concrete screeds, and waste pipes embedded in walls can all develop leaks that only show as damp patches on a floor or ceiling one flat away from the actual source. Thermal imaging is particularly effective here — it shows the temperature differential where the warm water pipe is leaking beneath the screed, distinguishing it from cold water or condensation.
How Thermal Imaging Finds Leaks in London Flats
Thermal imaging cameras detect temperature differences as small as 0.05°C — enough to see the heat signature of a warm water pipe leaking behind a plasterboard wall or under a wooden floor. The technique works best where there's a meaningful temperature difference between the leaking water and the surrounding structure: a hot water pipe at 55–65°C leaking under a concrete floor at 18°C shows up clearly. Cold water pipes at ambient temperature are more challenging — we often combine cold water pipe surveys with moisture meter readings to confirm location.
In purpose-built London flats — where leaks in one property frequently manifest as damp in the flat below — thermal imaging allows us to trace the moisture pathway back to the source without opening up either flat. A typical cross-flat leak survey takes 2–3 hours: we survey the affected (damp) flat first to establish where the moisture is entering from, then survey the flat above to find the temperature anomaly at the source pipe. This approach avoids the costly and contentious process of opening up walls in the wrong property.
Thermal imaging has limitations: it cannot see through thick concrete (more than 50mm of screed significantly attenuates the signal), and it requires the defective pipe to be running during the survey to produce a temperature differential. We schedule surveys to coincide with hot water system operating times and can request that heating is turned on before our arrival in cold water surveys.
"Thermal imaging cameras detect temperature differences as small as 0.05°C — enough to see the heat signature of a warm water pipe leaking behind a plasterboard wall or under a wooden floor.
Tracer Gas Leak Detection — The Most Accurate Method
Tracer gas detection uses a harmless mixture of 5% hydrogen and 95% nitrogen — an inert, non-flammable, non-toxic gas that's lighter than air. The pipe is isolated, depressurised, and the tracer gas introduced at one end under low pressure. The gas escapes at the leak point and migrates upward through concrete, screed, soil or road surfacing. A sensitive handheld probe (accurate to 1 part per million of hydrogen) detects the gas at the surface, pinpointing the leak to within 5–10 centimetres horizontally.
This is the method we use when thermal imaging or acoustic detection has identified the area of a leak but not the precise point — or when the pipe is buried too deep for thermal detection. Tracer gas is particularly effective on water mains buried under London driveways and paths, where acoustic signal is attenuated by the surrounding material and thermal imaging can't penetrate the surface. A tracer gas survey typically locates the leak within 10–15 centimetres, which minimises the excavation area for repair.
The main requirement for tracer gas is that the pipe can be isolated and the water removed so the gas can enter. For live mains in continuous use, we carry out the survey in two stages: a night survey (when demand is lowest and the pipe can be isolated briefly) followed by daytime confirmation. For domestic supply pipes in residential properties, we can usually carry out the full survey within a 2–3 hour appointment without significant inconvenience.
"Tracer gas detection uses a harmless mixture of 5% hydrogen and 95% nitrogen — an inert, non-flammable, non-toxic gas that's lighter than air.
What Our Leak Detection Report Contains — and Why Insurers Accept It
Our leak detection reports are structured to meet the documentation requirements of UK home insurers handling escape-of-water claims. The report includes: the survey methodology used; annotated thermal images or acoustic data plots showing the leak location; moisture meter readings at the source and adjacent areas; the precise leak location (described in relation to fixed reference points — measured distances from walls and floor); our assessed cause of the leak (sudden pipe failure, long-term corrosion, previous repair failure, etc.); and our recommended repair method.
The 'assessed cause' section is critical for insurance purposes. UK home insurance policies typically cover 'sudden and unforeseen' water escape but exclude 'gradual deterioration'. Our cause assessment distinguishes between these — green mineral deposits consistent with slow seepage look different under thermal imaging to the rapid moisture spread of a sudden pipe burst. We note our observations specifically to give the insurer the evidence they need to process the claim.
Reports are delivered in PDF format within 24 hours of the survey (same-day for emergency surveys). We name the report to your insurer's specific requirements where requested. Our reports are accepted without challenge by Aviva, Direct Line, AXA, NFU Mutual, LV=, and other major property insurers — we've developed our format in direct consultation with loss adjusters.
"Our leak detection reports are structured to meet the documentation requirements of UK home insurers handling escape-of-water claims.
Equipment We Use
- ✓ FLIR E8 thermal imaging camera (0.05°C sensitivity)
- ✓ Sewerin Aquaphon A200 acoustic leak detector
- ✓ TraceaTec hydrogen/nitrogen tracer gas equipment
- ✓ Digital moisture meter (Protimeter Surveymaster)
- ✓ Endoscope camera (15m flexible cable)
- ✓ Pressure decay test gauge set (0–10 bar)
- ✓ Correlator leak detection unit (long-range mains surveys)
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📞 Call 020 0000 0000Recent Jobs Across London
Kensington, W8 · Victorian mansion flat
Water bill doubled over 3 months — no visible damp, no sound of running water anywhere in flat
Tracer gas survey located pinhole in buried supply pipe under kitchen screed. 0.6m targeted screed removal and pipe replacement.
£580 (survey £280 + repair £300)Islington, N1 · 1990s purpose-built flat (4th floor)
Persistent damp patch on 3rd floor ceiling — 3rd floor resident's plumber found nothing wrong
Thermal imaging from 4th floor found warm moisture pattern under bath panel. Loose compression joint on bath waste — fixed in 30 minutes after detection.
£245 (detection + repair)Dulwich, SE21 · Detached Victorian house
Underfloor heating zone 2 cool — floor warm in some areas, cold in others
Thermal imaging + tracer gas located micro-fracture in underfloor loop under hallway tiles. Targeted tile removal and pipe repair. 4 tiles replaced.
£680 (survey + repair + tiling)Canary Wharf, E14 · Modern apartment (2015 build)
Insurance escape-of-water claim — insurer required detection report before approving remediation
Acoustic survey located pinhole leak in hot water pipe inside partition wall. Report submitted to Aviva. Claim approved 2 days later.
£320 (survey only — repair by insurer's contractor)London Coverage Map
Engineers stationed across all 33 London boroughs — North, South, East, West and Central London covered 24/7.
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Thermal · acoustic · tracer gas · all 33 boroughs in Every London Borough
Find local engineers and pricing for your specific borough — same service, local response times.
Standards & Compliance
Gas Safe
All gas work carried out by Gas Safe Registered engineers (Reg. 123456). We can provide copies of our Gas Safe certificates on request.
Water Regs 1999
All plumbing installations comply with the Water Supply (Water Fittings) Regulations 1999, including notification to the water undertaker for notifiable work.
Building Regs
Domestic plumbing and heating installations comply with Approved Document G (Sanitation, hot water safety) and Approved Document J (heat-producing appliances).
BS EN 805:2000
Water supply — requirements for systems outside buildings. Governs inspection and testing of water mains and service connections — relevant to buried water main leak detection and repair.
BS 6700:2006
Design, installation, testing and maintenance of services supplying water for domestic use — specifies pressure test methods used to confirm pipe integrity after leak repair.
CIBSE TM21
Minimising pollution at buildings — guidance on identifying and rectifying internal leakage in building services, referenced in our survey methodology for commercial properties.
We Cover All 33 London Boroughs
Engineers are stationed across London for fast response in every borough. Click your area for local information.