Leak Detection London — Non-Invasive Thermal, Acoustic & Tracer Gas
Locate hidden leaks across London using FLIR thermal imaging, Sewerin acoustic correlation and hydrogen tracer gas — without lifting floors or breaking walls. Insurance-grade ABI-format reports from £180. Same-day attendance, repairs available on the same visit.
Trace-and-access covered by most UK buildings policies. We deal direct with your insurer.
Non-invasive leak detection in London costs £180–£750 depending on methodology. Thermal imaging surveys start at £180, acoustic correlation £280, tracer gas testing £320 and a full insurance-grade ABI report from £450. Most leaks are pinpointed within 90 minutes and your buildings insurer typically covers the trace-and-access cost in full under standard escape-of-water cover.
Hidden leak detection across London
A hidden water leak rarely announces itself. The first sign is usually an unexplained spike in a Thames Water bill, a stained ceiling, a boiler losing pressure every few days, or a damp patch that grows during the day. By the time the symptom is visible the leak has often been running for weeks — and the secondary damage to plaster, screed, insulation, joinery and electrics is already 10× the cost of the original pinhole.
Non-invasive leak detection puts a stop to that. Using FLIR thermal imaging cameras to IRT Cat 1 standard, Sewerin SeCorr 300 acoustic correlators on buried mains, hydrogen tracer gas under concrete slabs, and Tramex / Protimeter moisture mapping across substrates, we pinpoint the source of a leak to within 50 mm — without lifting tiles, breaking plaster or excavating screed. The single 10 mm endoscope pilot hole that confirms the diagnosis is the only disturbance until the source is proven.
If the active escape is already pouring water through a ceiling, jump straight to our 24/7 emergency plumber line — minutes matter at mains pressure. Otherwise, call 0207 046 1363 for a same-day detection booking across all 32 London boroughs.
Detection methods we use
No single method finds every leak. The skill is in choosing the right tool first — based on symptoms, property type and the water service involved — and combining methodologies so that nothing is left to guesswork.
Thermal Imaging (IRT Cat 1)
FLIR T540 and E96 cameras to IRT Cat 1 (Level 1 thermographer) standard — pick up temperature deltas as small as 30 mK across walls, floors and ceilings. Works for hot and cold water leaks and underfloor heating.
Acoustic Correlation
Sewerin SeCorr 300 ground microphones and pipe correlators amplify the vibration of water escaping pressurised mains. Best for buried supply pipes and rising mains up to 6 bar.
Tracer Gas (Hydrogen 5/95)
Industry-standard hydrogen/nitrogen mix injected into an isolated circuit. The gas migrates through any breach and is picked up by a sniff probe — accuracy to within 50 mm even under concrete.
Moisture Mapping
Tramex Compact and Protimeter MMS3 capacitance meters quantify how wet a substrate is and chart the moisture gradient back to the source.
Salt-Trace and Dye
Fluorescein dye and salt-trace electrolyte are used to confirm waste, overflow, condensate and rainwater pathways without dismantling — vital when a wet ceiling could be one of four pipes.
Endoscope / Bore Camera
Flexible 6 mm and 9 mm bore cameras inserted through 10 mm pilot holes to confirm a suspected source before any plaster or tiling is removed.
Leak detection cost in London — 2026 prices
Prices are fixed on the call before any engineer attends. There are no parking charges within the Congestion Zone, no out-of-hours premium on scheduled work, and no separate VAT line — the figure you are quoted is the figure you pay. Same-visit repair is itemised separately so your insurer can pay the trace-and-access under the correct heading on your buildings policy.
| Service | What's Covered | Typical Cost | Time |
|---|---|---|---|
| Thermal imaging survey (single property) | FLIR T540 / E96 IRT Cat 1 scan of suspected wet areas, written photo report. | £180–£320 | 1–2 hours |
| Acoustic correlation (mains supply) | Sewerin SeCorr 300 correlator on incoming main, garden runs and risers. | £280–£420 | 2–3 hours |
| Tracer gas test (hydrogen 5/95) | Pressure-purge of suspect circuit with hydrogen/nitrogen mix, sniff survey. | £320–£480 | 2–3 hours |
| Salt-trace / dye test | Fluorescein or salt injection used to confirm waste, overflow or roof tracking. | £180–£280 | 1–2 hours |
| CCTV drain camera survey add-on | Push-rod or crawler camera with MSCC5 report — bolt-on to leak visit. | £180–£320 | 1–2 hours |
| Full insurance-report package | Combined thermal + acoustic + tracer gas + ABI-format report with photos and Cat coding. | £450–£750 | 3–5 hours |
| Leak detection + same-visit repair | Detection plus on-the-spot repair of accessible leak (1m of pipe, joint or fitting). | £380–£780 | 3–5 hours |
| Underfloor / under-screed leak | Wet UFH circuit isolation, manifold pressure test, thermal + tracer combined. | £420–£680 | 3–5 hours |
* Prices include VAT. Full pricing list on the pricing page.
Get a fixed quote in 5 minutes
Describe the symptom — we'll quote the right methodology and a same-day arrival window.
Call 0207 046 1363Signs of a hidden leak
A leak rarely shows itself in one obvious way. London's mix of Victorian terraces, Edwardian conversions, ex-council blocks, mews properties and new-build developments each fail differently. These are the symptoms we are called to most often — any one is enough to book a survey, two together is near-certain evidence of an active escape.
- Unexplained spike in your water bill. A 1 mm pinhole on a 4 bar main wastes around 3,500 litres a day — Thames Water billing picks it up before damp does.
- Damp patches on walls, floors or ceilings. Especially patches that grow during the day or change shape after a hot shower or full bath.
- Running-water sound when every tap is off. Sit in the loft hatch on a quiet night — a faint hiss is usually a mains pinhole, a drumming is usually an overflowing cistern.
- Warm spots on the floor. Almost always a hot-feed leak or an underfloor heating breach. Thermal imaging confirms in minutes without lifting any tile.
- Drop in mains water pressure. Sudden drops point to a buried supply pipe leak between the boundary stopcock and the kitchen tap — common in Victorian properties with lead and galvanised tails.
- Water meter ticking with no use. Isolate the property stopcock, watch the meter for 15 minutes — any movement at all is escape. We chart the test on the report.
- Mould or mildew in unusual locations. Behind a wardrobe on an internal wall, around a skirting on the ground floor, the underside of a stair string — these are leak shapes, not condensation shapes.
- Boiler losing pressure repeatedly. Top-up needed more than once a fortnight points to a system leak, often on a buried pipe or an underfloor circuit.
- Stained or bubbling paintwork. Tide-mark stains on a ceiling rose, brown paint blistering above a skirting — both flag a slow long-term escape.
- Sudden insurance-claim history on the block. If a neighbour has had an escape of water claim, the same pipe run almost certainly serves your flat too. Get ahead of it.
How a leak detection visit runs
A typical London visit takes 3–5 hours from arrival to a written report in your inbox. The structure below is what every detection booking follows — no extras, no surprises, no per-hour clock running while the engineer thinks about what to do next.
Phone triage
5 minutesCall 0207 046 1363 and our coordinator runs through symptoms, property type, suspect area and timeline. You get a fixed-price quote and an arrival window before you hang up.
Site inspection and isolation
20–30 minutesEngineer arrives, walks the property, isolates the cold main and tests at the meter to confirm whether the leak is internal supply, waste, central heating or rainwater. Methodology is chosen before any kit comes out.
Non-invasive detection
1–3 hoursThermal imaging, acoustic correlation, tracer gas and moisture mapping applied in the order most likely to find the source quickest. Findings narrated live so you understand what is being ruled in and out.
Pinpoint and pilot hole
10–20 minutesOnce a source is identified within 50 mm, a 10 mm endoscope hole is drilled in the least visible spot to confirm visually. No plaster off, no floor up, until the source is proven.
Repair or report
1–4 hoursIf access is straightforward we repair on the same visit. If not, you receive a written ABI-format insurance report with photos, thermal screenshots and recommended trace-and-access scope for your insurer.
Standards, qualifications and insurance recognition
Leak detection is unregulated as a trade — anyone with a camera can call themselves a leak detection company. The standards that matter are the ones your insurance loss adjuster recognises. Reports outside those standards get rejected, which leaves you paying for both the survey and the buildings claim out of pocket. Every methodology we use is calibrated to the standards below.
IRT Cat 1 Thermographer Certification
Lead engineer holds the InfraRed Training Centre Level 1 thermographer certificate — the minimum standard accepted by most UK insurers for thermal evidence in escape-of-water claims.
ABI Trace-and-Access Format
Reports follow the Association of British Insurers' trace-and-access template — claim cause, location, methodology, cost of detection separated from cost of repair. Compatible with Aviva, AXA, Direct Line, LV=, Hiscox, NIG and Allianz.
Water Regulations Approved (WRAS)
All temporary connections, gas injection ports and pressure test rigs are WRAS-compliant — no risk of contaminating your incoming main during testing.
BS EN 12056 (drainage) and BS EN 806 (supply)
Detection methodology aligns with the European drainage and water supply standards used by your buildings insurer's loss adjuster.
Calibrated test equipment
FLIR, Sewerin, Tramex and Protimeter instruments calibrated annually to manufacturer specification — calibration certificates kept on the van and quoted on every report.
£5M Public Liability Insurance
Aviva-backed £5,000,000 public liability and £2,000,000 professional indemnity. Cover details supplied with every quote on request.
Real London cases — what detection actually looks like
Every London property fails differently. Six recent jobs across the boroughs, anonymised — addresses changed, methodology and pricing real.
Victorian terraced 3-bed, Camden — kitchen ceiling stain
Scenario: Bathroom directly above the kitchen, stain 200 mm across, growing over 5 days. Two previous plumbers had quoted £1,800 to lift the bathroom floor.
Result: Thermal scan of the kitchen ceiling at 2 hours after morning shower picked up a cool spot 600 mm from the bath waste. Endoscope through a 10 mm pilot hole confirmed a failed compression on the bath trap — replaced in 40 minutes. Total cost £240, no bathroom floor disturbed.
Edwardian conversion flat, Islington — meter spinning
Scenario: Tenant reported a faint hiss in the kitchen wall, landlord's water bill had doubled in two quarters. Property had a polybutylene cold-feed installed in the 1990s.
Result: Acoustic correlation across the boundary stopcock, the kitchen riser and the bathroom riser triangulated the leak to a 200 mm section of polybutylene behind the kitchen base unit. Cut out, replaced with copper, pressure tested at 6 bar. Insurance report issued for the buildings policy. £420 total.
1970s ex-council flat, Southwark — warm floor
Scenario: Owner-occupier flagged a warm 600 mm circle in the hallway. No visible damage, no smell. Suspected hot-feed leak under the screed.
Result: Thermal imaging confirmed a 4°C delta over the warm area. Tracer gas injected into the hot supply leg, sniff probe found the breach within 30 minutes. Single 100 mm tile lifted, leak repaired. Owner-occupier insurance reimbursed trace-and-access at £480, separate from the £190 repair.
Mews house, Kensington — boiler losing pressure
Scenario: Worcester Bosch combi needing top-up every 4 days. No visible leak, no radiators showing damp on the wall behind them. Suspected underfloor heating breach.
Result: Manifold pressure test isolated to zone 3 (kitchen). Thermal map of zone 3 against the unheated zones showed a cold spot under the island — confirmed as a screw through a UFH pipe from a previous kitchen installation. Pipe sleeved and rerouted. Insurer accepted full trace-and-access of £620 and repair of £880.
Top-floor flat, Tower Hamlets — wet ceiling, leaseholder dispute
Scenario: Wet patch on the kitchen ceiling, flat above denied any leak. Managing agent needed evidence before instructing the upstairs leaseholder to allow access.
Result: Salt-trace dye injection through the upstairs flat's kitchen sink trap (with permission via the managing agent) was picked up on a moisture map of the lower flat ceiling within 90 minutes. Written report sustained a Section 152 access request — repair completed two days later. £380 detection, £0 dispute.
New-build 2-bed, Wandsworth — under-warranty leak
Scenario: Two-year-old block, leaseholder reported damp on the bedroom wall. NHBC warranty in play, developer asked for independent leak detection report before authorising rectification.
Result: Thermal and tracer gas confirmed a failed push-fit on the cold riser inside the partition wall — installation defect under the NHBC 2-year defects period. Report submitted to NHBC and developer paid both detection (£340) and full reinstatement (£1,420). Leaseholder out of pocket: nothing.
Areas covered — all 32 London boroughs
Detection vans are based across central, north, east and south London for same-day response. Heaviest call volumes come from Camden, Westminster, Islington, Hackney, Tower Hamlets, Southwark, Lambeth, Wandsworth, Hammersmith & Fulham, Kensington & Chelsea, Haringey and Greenwich.
Frequently asked questions about leak detection in London
How much does leak detection cost in London?
How does non-invasive leak detection actually work?
Is leak detection cheaper than just digging up the floor?
Will my insurance pay for leak detection?
How long does it take to find a hidden leak?
What are the common signs of a hidden water leak?
Can you find leaks under concrete floors?
Can you find a leak in a flat where the source is upstairs?
Do you provide reports suitable for insurance claims?
Do you use thermal imaging, acoustic or tracer gas — which is best?
Are your engineers qualified to inspect leaks for insurance purposes?
What happens if you can't find the leak?
Can you fix the leak the same day you find it?
What if the leak is on the shared water main, not inside my property?
Do you cover all London boroughs?
Question not answered above?
Call 0207 046 1363 — a coordinator (not an answering service) will talk through the symptoms and quote a methodology in under 5 minutes.
Book leak detection today
Same-day attendance across all 32 London boroughs. Fixed price confirmed on the call. Insurance-grade ABI report within 24 hours. £5M public liability, IRT Cat 1 certified thermographer. Detection from £180 — trace-and-access usually paid in full by your buildings insurer.
Fully insured · IRT Cat 1 thermographer · ABI-format reports · 24/7 London coverage
Service area
Leak detection across every London borough
Detection vans cover all 32 London boroughs plus the City of London — same-day response inside the M25, evening and weekend slots available across central, north, south, east and west London.