Safety first — call this first by situation

Active flooding right now. This page is for hidden leaks. For visible bursts or active flooding, see Burst Pipes Lambeth.

Smell gas, hear hissing or suspect a gas leak. Do not switch anything on or off, and do not use flames, electrical appliances, or smoke. Leave the property if the smell is strong, then call the gas emergency service on 0800 111 999 (free, 24/7) from outside.¹ Open windows and doors only if it is safe to do so.

Burst water main in the street, or supply has failed across a whole block. Call Thames Water on 0800 316 9800 (24/7).²

Right page for your problem?

This page is for hidden leaks — leaks you suspect but can’t see, unexplained water bills, damp patches with no visible source, Thames Water leak letters, and insurance-driven trace-and-access investigations. For other situations:

• Visible burst pipe or active flooding → Burst Pipes Lambeth
• Boiler leaking from the appliance itself → Boiler Repair Lambeth
• Heating system leak (radiator, valve, hidden pipe under floor on the heating side) → Central Heating Repair Lambeth
• Recurring drain/sewer issue, not a fresh-water leak → Blocked Drains Lambeth
• Active gas leak → call 0800 111 999¹

Quick routing: unexplained high water bill, damp patch with no visible source, or a Thames Water letter saying you may have a leak → leak detection. Hidden leak suspected by your insurer → “trace and access” — the engineer should know the term.

Signs you have a hidden leak

Per Thames Water’s Leaks at home guidance, the frequent signs of a hidden leak are damp patches, low water pressure, and higher bills if you’re on a meter. You may also receive a letter or email from Thames Water if their network monitoring detects a leak at your property.²⁷

Per Thames Water’s Customer Side Leakage Code of Practice, other tell-tale signs include reduced water flow or pressure at the cold kitchen tap, waterlogged or damp areas in the garden during dry weather, and noisy pipes.²³

A simple at-home check before you call:

1. Meter test (if you’re on a meter): turn off every tap and appliance using water — including toilets, washing machines, dishwashers, and outside taps. Don’t use any water during the test. Take a meter reading, then read it again 30 minutes later. If the dial moves, there may be continuous flow somewhere — often a leak.
2. Toilet test: put a few drops of food colouring in the cistern (not the bowl). Wait 30 minutes without flushing. If colour appears in the bowl, the flush valve is leaking — a frequent silent waste.
3. Stop tap test: with all taps off, turn the internal stop tap off. If the meter still moves, it may indicate a leak before the internal stop tap, such as on the supply pipe. Shared supplies, meter location, and property layout can affect this. If the meter stops, the leak may be inside the property or after the internal stop tap.

These checks narrow the search. A leak detection engineer can help narrow down or identify the suspected source.

What leak detection involves

There’s no single technique that finds every leak. Engineers often use a combination, depending on what’s accessible and where the leak is suspected:

• Acoustic listening equipment — surface-mounted sensors that pick up the sound of water escaping under pressure. Useful for pressurised supply pipework.
• Thermal imaging cameras — show temperature differences on walls and floors, which can reveal hot water leaks (warmer) and cold leaks (cooler) below the surface.
• Specialist tracer gas — introduced to the empty pipework; it escapes through any leak point and is detected at the surface with a sniffer.
• Pressure testing — isolating a section of pipework and pressurising it to confirm the leak is in that section.
• Moisture mapping / damp meters — measure moisture levels in walls, floors and substrates to localise the wettest area.

For waste/drain leaks only — not fresh-water pipework — engineers may also use CCTV pipe inspection, where a camera on a flexible rod inspects the inside of the pipe.

A leak detection visit is indicatively 1–3 hours, depending on access and complexity. Ask whether the engineer will provide a written report identifying the suspected leak location — insurers may ask for this.

Non-destructive methods are the goal but not always achievable. If the leak is deep under solid floors, behind tiled walls, or in inaccessible voids, some opening up may be needed even at the detection stage. Confirm in advance whether the engineer will reinstate any opened areas or whether that’s a separate trade.

When you call

Before the engineer travels, get the following in writing (a text or email is fine):

• Callout fee — and what it includes
• Hourly rate or fixed-fee structure — leak detection is more often quoted as a fixed visit price than as hourly
• Methods used — does the engineer carry acoustic, thermal and tracer-gas kit, or only some of these?
• Report — will a written report be provided? Insurers may ask for this.
• Repair scope — will the same engineer quote for the repair, or is it referred on?
• Reinstatement — if any opening up is needed, who reinstates flooring, plaster or tiles?

Have ready when you call: approximate location of damp/staining (which room, ceiling/wall/floor), how long you’ve noticed it, your latest meter reading and the previous one if you have it, any letter reference from Thames Water or your insurer, and your postcode.

High water bill or Thames Water leak letter

If you’ve received a letter from Thames Water saying their monitoring suggests a leak at your property, you have a defined process to follow.

Per Thames Water’s Leaks at home guidance, once a leak is discovered at your property, you are expected to arrange repair within four weeks.²⁷ If the leak is on Thames Water’s side of the boundary, they fix it. If it’s on your side (boundary stopcock to property, all internal pipework), it’s your responsibility per Thames Water’s pipe responsibility guidance.⁷

Leak allowance — what may be available

Per Thames Water’s leak allowance page, if you have a water meter and you fix the leak within the published timeframe, Thames Water may credit your account for the lost water.²⁸

To claim, Thames Water typically requires:

• Confirmation the leak is fixed — a plumber’s invoice with their details, or a Thames Water job number if they did the repair
• That the leak wasn’t fixed under Section 75 of the Water Industry Act 1991 (i.e. you fixed it voluntarily, not after Thames Water stepped in)
• The claim is made within Thames Water’s published deadline from the repair date²⁸

Keep the leak detection report, the plumber’s invoice for the repair, and the meter readings before and after — Thames Water will need these.

What if I don’t fix it?

Per Thames Water, if a leak isn’t fixed within their stated timeframe, they may carry out the repair themselves under Section 75 of the Water Industry Act 1991 and charge the homeowner.²⁷ ²⁹

Section 75 gives water undertakers the power to serve notice on the consumer where water is being or is likely to be wasted, requiring steps to stop the waste — and, in cases that constitute an emergency, to disconnect the supply.²⁹

Arrange investigation and repair promptly within Thames Water’s stated timeframe.

Insurance and trace-and-access

Some home insurance buildings policies may include “trace and access” cover, often subject to limits and conditions — this is the cost of finding the source of a leak (and reinstating any opened areas) so the underlying problem can be fixed. Check your policy wording before instructing.

Trace-and-access cover, where included, may be subject to limits and conditions, which vary by insurer. It may apply where a leak has caused escape-of-water damage but the source isn’t visible.

Practical steps if you’re claiming on insurance:

• Notify the insurer as soon as practicable — most policies have a notification deadline.
• Ask the insurer whether they have a preferred trace-and-access process — some require a specific contractor or report format. If you instruct your own engineer first and the insurer disputes the cost, you can be left out of pocket.
• Get a written report from the leak detection engineer detailing methods used, location of the leak, and recommended repair scope.
• Photograph everything — damp patches, stained ceilings, floors, possessions affected.
• Don’t dispose of damaged items until the insurer has had a chance to inspect or you’ve been told you can.

Insurance treatment of trace-and-access varies by policy. Read your wording before instructing.

Lambeth-specific signals

Conversion flats and leaks across boundaries

Victorian and Edwardian conversion flats are common across Brixton, Clapham, Stockwell, Herne Hill, Tulse Hill, Streatham and West Norwood. Leaks in conversion flats can cross flat boundaries — water from a flat upstairs appears on the ceiling below.

Leak detection in this context often involves three things at once: locating the leak, agreeing access with the upstairs occupier, and establishing whose responsibility the source pipework is. For shared cold mains and communal stacks, the freeholder or managing agent is normally involved. Always refer to your individual lease, which overrides general guidance.

Underground supply pipe leaks

In Lambeth’s older terraced and converted housing, suspected underground supply-pipe leaks may present as continuous meter movement with no internal damp visible — the supply pipe runs invisibly under the front garden or driveway.

Detecting these leaks often involves acoustic and tracer gas methods. Repair often uses moling (a trenchless technique) to install a new MDPE pipe without digging up the full length — useful for properties with paved or block-paved frontages. Per Thames Water’s Customer Side Leakage Code of Practice, where reinstatement of decorative surfaces (block paving, crazy paving) is involved, the homeowner may need to arrange specialist reinstatement separately.²³

Lead supply pipes

Some Victorian and Edwardian Lambeth properties may still have lead supply pipes from the boundary to the house. Lead supply pipes are a recognised water-quality issue, and a leak detection visit on suspected lead pipework is often the precursor to a wider conversation about full replacement rather than spot repair.

Replacement may be recommended depending on condition, access and cost. Get two written quotes; this is rarely a same-week decision.

Conservation areas

Per Lambeth Council, the borough has 62 designated conservation areas covering approximately 30% of its area.⁸

Much leak detection work is internal and non-destructive. But if a leak detection finding leads to external excavation in a conservation area — particularly affecting front-elevation supply pipework or other visible external features — check whether planning advice is needed. Routine like-for-like repair and reinstatement do not normally engage planning permission. Lambeth Council administers these as the local planning authority.

Lambeth council tenants and leaseholders

Per Lambeth Council’s repair responsibility guidance, the Council is responsible for keeping fixed pipes, water tanks, and waste pipes in good working order in council-owned homes.⁹

If you’re a Lambeth council tenant and you suspect a hidden leak:

• Working day repair: 020 7926 6000, or via your online tenant account.¹⁰
• Out-of-hours emergency repairs: 020 7926 6666 — for issues classified as emergencies by Lambeth Council, such as total loss of mains water supply.³ ¹⁰

A hidden leak — damp patch, mystery water bill — is often a working-day repair request rather than an emergency callout.

If you book a private engineer instead of going through the Council, you may not be reimbursed unless the repair was authorised or Lambeth policy allows it.

Leaseholders of former council flats: pipework inside your demised premises is typically your responsibility under the lease, per Lambeth’s leaseholder repair guidance.¹² Communal stacks and cold mains are usually the freeholder’s. Always refer to your individual lease.

Private renters and landlords

Per Section 11 of the Landlord and Tenant Act 1985, every short-lease residential tenancy contains an implied covenant by the landlord to keep in repair the installations for the supply of water, gas, electricity and sanitation, and the installations for space heating and water heating.¹³ A hidden leak in a rented home is likely to engage Section 11 repair duties.

Tell the landlord (or letting agent) immediately and in writing as soon as you notice damp patches, unexplained sounds, or higher-than-expected water charges. Keep a copy of every message.

If the landlord won’t act and damp damage is increasing, you can contact Lambeth Private Sector Housing where licensing or housing-condition enforcement applies. In the moment, a directory-listed engineer can investigate; reimbursement is then a separate conversation.

Selective licensing

Lambeth’s Selective Licensing Scheme currently applies to many privately rented homes in the borough — typically those let to a single-family household or no more than two unrelated sharers — across most wards, with Vauxhall and Waterloo & South Bank excluded.¹⁴ Coverage is subject to ward designation, property-level exemptions, and change.

Check current status with Lambeth Council before relying on this — designations are time-limited. HMOs continue to be licensed separately under the Council’s HMO licensing schemes. A licensed landlord must keep the property in good repair as a licence condition.

What does leak detection cost in Lambeth?

Indicative directory estimates only, based on London plumbing market familiarity — not regulated rates and not official market data. No official pricing data exists for private leak detection.

Always confirm pricing before work begins. Actual costs vary by access, premises type, leak complexity, methods required, and whether a written report for insurance is needed. VAT applies. Reinstatement of opened areas is normally a separate trade.

The leak detection cost is separate from the repair. Once located, the repair is normally quoted on its own — burst pipe, joint replacement, supply pipe replacement, or specialist work depending on the finding.

For repair cost ranges, see the Burst Pipes Lambeth cost section.

Lambeth-specific cost factors:

• Conversion flat access — leak investigations involving the flat above can require neighbour cooperation and shared-stack access; common across Brixton, Stockwell, Streatham, Tulse Hill and West Norwood conversion flats.
• Underground supply pipe investigations — properties with paved or block-paved frontages may attract higher reinstatement costs separate from the detection itself; specialist reinstatement of decorative surfaces is often a separate trade.
• Conservation areas — if a finding leads to external excavation on a front elevation in one of Lambeth’s 62 conservation areas, check whether planning advice is needed before any visible external pipework changes; routine like-for-like repair and reinstatement don’t normally engage planning permission.
• Modern new-builds (Vauxhall, Nine Elms) — communal risers and the building’s mains supply are typically the building operator’s; a private engineer called for what turns out to be a communal-side leak may incur a callout fee for a visit they cannot complete.
• Lead supply pipe properties — older Lambeth properties with lead supply pipes can lead to a full pipe replacement quote rather than spot repair, which is a more substantial job.

Why directory-listed engineers

Under the Gas Safety (Installation and Use) Regulations 1998 (enforced by HSE), any gas work on a domestic gas appliance must be carried out by a Gas Safe registered engineer competent for that category of work, with registration through the Gas Safe Register.⁵ ¹⁵ Leak detection does not usually require Gas Safe registration unless gas appliances or gas pipework are involved.

Before any engineer appears in this directory we check, at minimum:

• Gas Safe registration for any engineer offering gas work, against the Gas Safe Register’s check an engineer service.⁵
• Public liability insurance — industry-standard rather than a legal requirement for plumbers, but every listing carries it at time of listing.
• Business identity — registered company details, trading name, and trading address.

Listing checks are point-in-time, completed at the time of listing. Gas Safe status should be checked again at booking.⁵

FAQs – Leak Detection Lambeth

Areas covered

Lambeth’s postcodes span 13 districts crossing central, south, and southeast London. Property type and pipework varies considerably by postcode — when you call, mention the postcode and the property type so the engineer can plan the right approach.

• SW2 — Brixton, Brixton Hill, Streatham Hill (parts). Includes older terraced housing, much of which has been converted into flats.
• SW4 — Clapham, Clapham Common, Clapham Park (parts). Includes period terraces and 1930s mansion blocks; Old Town area includes listed properties.
• SW8 — South Lambeth, Stockwell (parts), Vauxhall (parts), Oval (parts). Includes period terraces, conversion flats, and modern new-build developments around Nine Elms and Vauxhall.
• SW9 — Brixton (parts), Stockwell (parts), Angell Town, Loughborough Junction (parts), Oval (parts). Includes period terraces and post-war housing.
• SW12 — Clapham Park (parts) (postcode crosses borough boundary into Wandsworth — confirm the property is in Lambeth before booking).
• SW16 — Streatham, Streatham Hill (parts), Streatham Vale. Includes period housing, mansion blocks, and post-war development along the High Road.
• SE1 — Waterloo, South Bank, Lambeth (North Lambeth) (parts), Vauxhall (parts). Includes modern blocks and converted commercial buildings.
• SE5 — Brixton (parts), Myatt’s Fields. Predominantly includes period terraces.
• SE11 — Kennington, Vauxhall (parts), Oval (parts). Includes a notable concentration of Georgian terraces, with listed properties.
• SE19 — Crystal Palace (parts), Gipsy Hill (parts). Includes older period housing.
• SE21 — Tulse Hill (parts), West Dulwich. Includes period housing with some later infill.
• SE24 — Herne Hill, Tulse Hill (parts), Loughborough Junction (parts). Mostly period housing.
• SE27 — West Norwood, Tulse Hill (parts), Gipsy Hill (parts). Includes period housing and post-war development.

Related services in Lambeth

• Burst Pipes Lambeth
• Emergency Plumber Lambeth
• Blocked Drains Lambeth
• General Plumbing Lambeth
• Boiler Repair Lambeth

Related guides

• How to Find Your Stop Tap (London Homes)
• London Plumbing Costs & Compliance Guide 2026
• How to Read a Plumbing Quote
• New Homeowner Plumbing Guide — London 2026

Closing

Hidden leaks are usually solved by accurate diagnosis rather than speed of response. The right call is the engineer who can locate the leak with confidence, document it for your insurer or Thames Water, and either repair it themselves or refer the repair cleanly.

Do the meter test and the toilet test before you call — they’re free, they take minutes, and they sharpen the brief you give the engineer.

Confirm the visit cost, the methods used, and whether a written report is included before the engineer travels.

For Lambeth landlords, keeping installations for water in repair is a Section 11 duty under the Landlord and Tenant Act 1985.¹³ Tenants without working installations can contact Lambeth Private Sector Housing where licensing or housing-condition enforcement applies. Lambeth’s Selective Licensing Scheme currently applies to many privately rented homes across the borough except in Vauxhall and Waterloo & South Bank wards — check current status with Lambeth Council before relying on this.

Contact directory-listed leak detection engineers in Lambeth ↑

← Back to all plumbing services in Lambeth

Last reviewed: May 2026 by Adiel Khan — SFEDI-accredited business advisor with 20+ years experience (South East Enterprise Ltd) and operator of VerifiedPlumbers. LinkedIn ↗

This page is reviewed against guidance published by HSE ↗, Gas Safe Register ↗, GOV.UK legislation ↗, Thames Water ↗ and London Borough of Lambeth ↗. The page draws on Thames Water pipe responsibility, leaks at home guidance, leak allowance process, Customer Side Leakage Code of Practice and incident reporting; Lambeth Council housing repairs, repair timescales, emergency contact numbers, Selective Licensing Scheme and conservation areas; Gas Safe Register registration and ID-card guidance; HSE engineer registration check, gas emergency contact and Gas Safety (Installation and Use) Regulations 1998 enforcement; and UK legislation (Landlord and Tenant Act 1985 Section 11; Water Industry Act 1991 Section 75).

Sources & further reading

¹ HSE — Domestic gas safety FAQ (gas emergency contact). https://www.hse.gov.uk/gas/domestic/faqs.htm ² Thames Water — Our incident guide. https://www.thameswater.co.uk/help/incident-guide ³ Lambeth Council — Emergency contact numbers. https://www.lambeth.gov.uk/about-council/contact-us/emergency-contact-numbers ⁵ Gas Safe Register — Check An Engineer. https://www.gassaferegister.co.uk/find-an-engineer-or-check-the-register/check-an-engineer/ ⁷ Thames Water — Pipe responsibility. https://www.thameswater.co.uk/help/water-and-waste-help/leaks/pipe-responsibility ⁸ Lambeth Council — Conservation area profiles. https://www.lambeth.gov.uk/planning-and-building-control/conservation-and-listed-buildings/conservation-area-profiles ⁹ Lambeth Council — Our repair responsibility. https://www.lambeth.gov.uk/housing/housing-repairs/tenants-repairs/our-repair-responsibility ¹⁰ Lambeth Council — Request a housing repair. https://www.lambeth.gov.uk/housing/housing-repairs/tenants-repairs/request-housing-repair ¹² Lambeth Council — Leaseholders and repairs. https://www.lambeth.gov.uk/housing/housing-repairs/leaseholders-repairs ¹³ Landlord and Tenant Act 1985, Section 11 — legislation.gov.uk. https://www.legislation.gov.uk/ukpga/1985/70/crossheading/repairing-obligations ¹⁴ Lambeth Council — Selective Licensing Scheme. https://www.lambeth.gov.uk/housing/landlords-licensing/selective-licensing-scheme ¹⁵ HSE — Check an engineer – are they Gas Safe registered? https://www.hse.gov.uk/gas/gas-safe-register-check.htm ²³ Thames Water — Customer Side Leakage Code of Practice. https://www.thameswater.co.uk/media-library/zfhokmwm/leakage-code-of-practice.pdf ²⁷ Thames Water — Leaks at home. https://www.thameswater.co.uk/help/water-and-waste-help/leaks/leaks-at-home ²⁸ Thames Water — Claim leak allowance. https://www.thameswater.co.uk/help/water-and-waste-help/leaks/leaks-at-home/leak-allowance ²⁹ Water Industry Act 1991, Section 75 — legislation.gov.uk. https://www.legislation.gov.uk/ukpga/1991/56/section/75