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Nitrogen tracer-gas regulator and gauges set up next to a bathroom sink during a leak-detection callout

Leak detection

Underground supply pipe leak across London

Specialist underground supply pipe leak as part of our 24/7 leak detection service. Same fixed pricing, same 30 to 60 minute target response, same 12-month guarantee.

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30 to 60 min target response12-month guaranteeGas Safe Registered
30-60 MINResponse time
12 MOWorkmanship guarantee
FULLYInsured & accredited
24/7365 days a year

Underground supply pipe leaks are among the most expensive plumbing failures to fix, not because of the repair cost itself, but because of the cost of finding the leak. Excavating a 30m run of front garden to locate a single pinhole in lead pipe can cost £5,000+ in groundworks alone, plus reinstatement of paving, drives or grass.

Our specialist underground leak detection team uses calibrated acoustic ground microphones (SewerIn Aquaphon A200) and tracer gas with surface sniffer probes to locate the precise failure point before excavation. A typical underground supply pipe trace pinpoints the leak to within 200,400mm, meaning we excavate a 1m square hole, not a 30m trench.

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When We Use This

Where this service applies

  • ✅ Lead supply pipes (Victorian/Edwardian London, typically 70,120 years old)
  • ✅ MDPE plastic supply pipes (post-1980s. Failures often at joints with old lead)
  • ✅ Copper supply pipes (pinhole corrosion in hard-water London)
  • ✅ Concrete/stone driveway supply pipe failures (precision finding crucial)
  • ✅ Garden lawn supply runs (avoid landscape damage)
  • ✅ Communal supply risers in apartment buildings
Our Process

How we deliver

No surprises, no upselling. The exact path every job follows.

  1. 1
    Pressure verification
    Confirm leak symptoms with pressure-decay test on isolated supply.
  2. 2
    Pipe-locator survey
    Electromagnetic locator maps the pipe route from stop-tap to property.
  3. 3
    Surface acoustic walk
    Ground microphones at 1m intervals along confirmed pipe route.
  4. 4
    Correlation analysis
    Two synchronised sensors used at run ends to triangulate leak position.
  5. 5
    Tracer gas verification
    Where acoustic isn't conclusive (plastic pipes), tracer gas surface scan.
  6. 6
    Marked-up location plan
    Spray-paint mark on surface. Written report with measured offsets.
  7. 7
    Excavation/repair quote
    Separate quote for the actual repair (or assignment to Thames Water if it's their side).
Frequently Asked

Your questions answered

Who's responsible for the underground supply pipe, me or Thames Water?
Generally: Thames Water is responsible for the run from the water main in the street to the boundary stop-tap. You (the property owner) are responsible from the boundary stop-tap to the internal stop-tap inside your property. Our leak survey identifies which side the leak is on, and if it's Thames Water's side we direct you to them (free repair) and don't charge for our investigation.
How much can an underground leak waste in water?
Even a small pinhole leak in a pressurised supply pipe wastes 1,000,5,000 litres per day continuously. At Thames Water tariffs that's £400,2,000 per year on your bill. Most undetected underground leaks have been running for 6+ months by the time the customer notices.
Will Thames Water investigate underground leaks for me?
Thames Water will investigate the public-side supply (from main to boundary) free of charge if you call them with bill evidence. They will not investigate the private-side supply (from boundary to property). That's where we come in.
How much does underground leak detection cost?
A standard residential supply pipe trace including locator survey, acoustic walk, written report and marked-up plan is priced per our published rate card (see full pricing). Complex traces with tracer gas verification are also priced per our published rate card.
Can my home insurance pay for the leak detection?
Most policies include trace-and-access cover (£5,10k) that covers leak detection costs even on supply-side leaks where the actual repair may not be covered. Worth checking your policy wording, we provide insurance-grade reports for direct claim.
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30 to 60 minute response across every London borough. Gas Safe registered. 12-month workmanship guarantee.

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FAQ

Underground supply pipe leak: your questions

How fast can you reach me for underground supply pipe leak?
Typical on-site time is 30 to 60 minutes across the M25, subject to engineer availability and traffic. Live dispatch, never queued. Times quoted are best-effort targets, not contractual guarantees.
What does underground supply pipe leak typically cost?
Labour is one flat rate across London and the M25, billed per 30 minutes: from £75 / 30 min (daytime) up to £147 / 30 min (nighttime), with a one-hour minimum then 30-minute increments. There is no callout fee. Domestic prices shown inc VAT, no hidden extras. Fixed-price conversion available on most jobs after diagnosis. Full rate card.
Is the work guaranteed?
Yes. Underground supply pipe leak carries the same 12-month workmanship guarantee as every other leak detection job we do.
Are you Gas Safe registered?
Yes. Gas Safe Register number 972173. Verifiable live at gassaferegister.co.uk before our engineer walks in.

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Need underground supply pipe leak now?

30 to 60 minute response across every London borough. Gas Safe registered. 12-month workmanship guarantee.

Call 020 8050 5306WhatsApp nowBook online