How do I know I've got a hidden leak and not just damp?

Tell-tale signs are a rising water bill with no change in use, the sound of running water when taps are off, a warm patch on the floor, often a heating-pipe leak, a persistent musty smell, or a drop in pressure. A meter test — shutting the internal stop valve and watching for movement — is a good first check, and a leak-detection survey confirms whether it's a leak and pinpoints where.

The damp is in one room but the plumber says the leak is elsewhere — how?

In a converted house or a period property, water tracks along ceiling voids, joists and under floors, so it often appears below a different room from the failed pipe. That's exactly why tracing the source beats opening up where the stain shows.

Thames Water wrote to say I have a leak — what now?

That usually means a leak on your supply pipe, which is the owner's responsibility. Their monitoring flags that a leak exists but not exactly where — often on the underground run across a front garden — and once confirmed you have a legal duty to repair it within four weeks, so accurate detection first is the sensible step.

Leak Detection in Eltham (SE9)

Q: I rent — should my landlord deal with a hidden leak?

Yes. Report it in writing; Royal Greenwich says serious hazards can be reported to its Residential Services team, and the council can step in where a landlord doesn't act.

A hidden leak shows as a stain, a smell of damp, a creeping water bill or a warm patch on the floor — rarely as an obvious burst. Finding it precisely matters in Eltham, where much of the stock is interwar, period or conservation-protected. Skip to verified plumbers ↓

✅ Checked before listing — identity, insurance, trading presence, Gas Safe (where relevant).
How we verify →
✅ Workmanship guarantee badges on listings — 1, 3, 6 or 12 months

⚠️ A hidden leak is a diagnosis before it’s a repair — the aim is to locate it so as little as possible is opened up. If water is actively flooding the home, that’s Emergency Plumber. Gas smell → National Gas 0800 111 999.

Contact verified plumbers in Eltham ↓

Are you a plumber covering Eltham?

Use the search above to find a local expert

Coverage: verified leak-detection plumbers across Eltham and the wider SE9 area — the town centre, Well Hall and the Progress Estate, Eltham Park, Eltham Green, Mottingham, New Eltham and Avery Hill.
What this covers: tracing hidden water leaks — under floors, behind walls, in heating circuits and on the underground supply pipe — with as little disruption as possible.
Not sure it’s leak detection? A pipe flooding the home now is Emergency Plumber; a known burst is Burst Pipes; an overflowing or blocked drain is Blocked Drains.
Costs: indicative detection ranges are under What it costs below — editorial estimates only.
Availability: each plumber sets their own hours, shown on their profile.

Jump to: Signs of a hidden leak · First checks · How leaks are found · Where they hide in Eltham · The Thames Water letter · Heritage & careful access · Leak or flood? · Who pays · Costs · FAQs

Signs you have a hidden leak

Hidden leaks announce themselves indirectly: a damp patch or tide-mark on a wall or ceiling; a musty smell that won’t clear; an unexplained rise in your water bill; the sound of running water when every tap is off; a drop in pressure; or a warm patch on the floor, which often points to a leak on a heating pipe below. Outdoors, a persistently damp patch or an unusually lush strip of lawn can mark a leak on the underground supply pipe.

Any one is worth investigating early. A slow leak into the fabric of an interwar Well Hall semi or a Victorian house does its damage quietly — softening plaster, rotting joists and staining brickwork long before it’s obvious — and the longer it runs, the more of the building has to be opened up to reach it.

First checks — before anyone opens anything up

Good detection is a sequence, not a guess. A verified plumber typically works from least to most intrusive: a meter test (read the meter, shut the internal stop valve for a period, re-read — movement points to a leak upstream of the isolation point); stop-tap isolation to narrow the leak to supply-side or internal; a pressure test on the suspect circuit; then damp mapping to locate where water has spread — and only then intrusive access, at the single most likely point rather than exploratory digging. That order is what keeps the repair small.

How a leak is found — without tearing the house apart

The point of leak detection is to locate the source precisely, so the repair disturbs as little as possible. A verified plumber has several non-invasive methods, chosen to suit the leak:

Acoustic detection — sensitive listening equipment picks up the sound of water escaping under pressure; useful for buried supply pipes and pipes under floors.
Thermal imaging — a camera reads temperature differences, tracing a warm heating-pipe leak or the cool track of escaping water across a floor or wall.
Moisture meters and damp mapping — pinpoint where water has spread, narrowing the search before anything is lifted.
Tracer gas — a safe gas is introduced into the pipework and detected where it escapes, isolating a leak an inch at a time; often the method of choice on a pressurised pipe when a heating circuit keeps losing pressure and topping up from the mains.
CCTV drain survey — used where the “leak” is actually on the waste or drainage side: a suspected cracked gully, a failed underground drain or a blocked waste pipe, rather than a pressurised supply leak.

The diagnostic step is what separates a fix from a guess. In Eltham especially, finding the exact spot means a targeted repair rather than an exploratory dig through interwar, period or protected fabric.

Where leaks hide in Eltham homes

Eltham’s housing shapes where leaks turn up. As a matter of local character, the area leans towards interwar suburban housing — the garden-suburb Progress Estate at Well Hall, 1920s–30s semis across SE9 — with Victorian and Edwardian pockets near the town centre, flats above shops along Eltham High Street, and modern flats in and around recent regeneration.

That mix produces recurring patterns. In interwar and period houses, leaks track under suspended timber floors and behind plaster — and in a converted house, water can run along a ceiling void and appear below a different room from the failed pipe, so the damp patch rarely marks the source. In converted or purpose-built flats, the first job is establishing whether the leak is from your own pipework, a communal riser, or the flat above before anyone opens up — which usually means coordinating managing-agent access. Heating-circuit leaks in older systems show as a slow pressure drop with the boiler topping up from the mains. And on semis with front gardens, the underground supply run from the boundary to the house is a common place for a hidden external leak. Hard water plays its part — Thames Water says all the water in its region is hard, and hard-water scale, pipe age, installation quality and corrosion can all contribute to the small pinhole leaks that are hardest to find and easiest to misdiagnose in older copper.

If Thames Water has written to you about a leak

Many supply-pipe leaks come to light not through damage but through a letter. Thames Water monitors usage and may contact you when it detects signs of a leak on your side of the boundary — but that notification means a problem may exist on your supply pipe, not an offer to fix it. The responsibility is clear: as the homeowner you’re responsible for the supply pipe from your boundary into the home, and once a leak is confirmed you have a legal duty to arrange the repair within four weeks.

That four-week clock is why precise detection pays: Thames Water’s monitoring can tell you a leak exists but not exactly where on your property it is, so locating it accurately — often on the underground run across a front garden or drive — is the job a verified leak-detection plumber does before any repair. If you’re a tenant, the leak is the landlord’s to fix — report it straight away. On Eltham’s older stock, a confirmed supply-pipe leak is also a prompt to check whether the pipe is lead: Thames Water notes homes built before 1970 may have lead supply pipes, and runs a replacement scheme where you replace the private section.

Heritage and careful access

Precise detection isn’t just a convenience in Eltham — it protects things that are hard to put back. Royal Greenwich’s conservation areas include Eltham Palace (1971), Eltham Green (1975), the Progress Estate and Well Hall Pleasaunce (1971), and the Progress Estate at Well Hall in particular is a designed garden-suburb whose external character is protected. Opening up a roof, a rendered elevation or an original feature to chase a leak is exactly the kind of work you want to keep minimal, and which may need care over consents. The right sequence is: detect first, then repair small — non-invasive tracing means the eventual repair opens up the least amount of protected fabric.

Is it a leak, or is it flooding or groundwater?

Not all water in a home comes from a pipe. Parts of the wider Eltham area sit within the Environment Agency’s “River Quaggy at Chinbrook, Mottingham and Eltham” flood-warning area, and Royal Greenwich’s flood assessment notes fluvial risk along the Quaggy corridor and surface-water risk in parts of the borough. Recurring water at floor level, damp that worsens after heavy rain, or water in a low-lying property near the Quaggy around Mottingham may be surface water or groundwater rather than a plumbing leak. A good leak-detection plumber will establish whether the source is a pipe at all before recommending a repair — and if it isn’t, you can check your address on the GOV.UK long-term flood-risk service and treat it as a flood-management matter.

Who pays — owner, leaseholder, tenant or council?

Owner-occupiers arrange and pay for detection and repair on their own pipework, internal and external up to the boundary. A trace-and-access clause in a home insurance policy sometimes covers the cost of finding the leak (and making good afterwards) — worth checking your policy before you commission work, and asking your plumber for a written leak-location report with photos and moisture readings to send to the insurer.

Council tenants go through Royal Greenwich: a leaking water or heating pipe is one of the council’s urgent repair categories, reported on 020 8921 8900 in the day or 020 8854 8888 out of hours. A leak the council is responsible for maintaining shouldn’t be a private booking.

Private tenants report to the landlord, who is responsible for the repair; Royal Greenwich says serious hazards such as sewage leaks or no hot water can be reported to its Residential Services team on 020 8921 8157, with 14 days for the landlord to respond to less serious issues first. Leaseholders and managed blocks — a leak in your own pipework is usually yours, while shared risers, communal pipework and the structure sit with the freeholder or managing agent, so establishing where the leak originates also establishes who pays.

What leak detection costs in Eltham

A rough orientation to sense-check a quote — not a price list, and not official market data.

Job	Typical indicative range	Notes
Leak-detection call-out / trace-and-access	£150–£400	Locating the leak, before repair
Acoustic or thermal-imaging survey	£200–£500	Depends on property size and access
Tracer-gas or CCTV drain survey	£150–£450	For pinhole or drain-side leaks
Underground supply-pipe leak location	£200–£600	External run from boundary to home

Editorial estimate only — not regulated rates, not official market data, and not a substitute for written quotations. A trace-and-access clause in home insurance may cover part of the detection and making-good cost.

Eltham is inside the London Ultra Low Emission Zone, so a non-compliant van may carry the £12.50 daily charge — check the current position.

Frequently asked questions

Tell-tale signs are a rising water bill with no change in use, the sound of running water when taps are off, a warm patch on the floor, a persistent musty smell, or a drop in pressure.

A warm patch on the floor is often a heating-pipe leak.

A meter test — shutting the internal stop valve and watching for movement — is a good first check.

A leak-detection survey confirms whether it’s a leak and pinpoints where.

Thames Water — leaks

The point of professional detection is to avoid that.

A plumber works least-to-most intrusive — meter test, isolation, pressure test and damp mapping.

They may use acoustic listening, thermal imaging and tracer gas to locate the source precisely.

That means the repair opens up as little as possible.

That matters in Eltham’s interwar, period and conservation-area homes.

In a converted house or a period property, water can track along ceiling voids, joists and under floors.

That means it often appears below a different room from the failed pipe.

That’s exactly why tracing the source beats opening up where the stain shows.

Often the first job is establishing whether the leak is from your own pipework, a communal riser or the flat above.

That usually means coordinating managing-agent access before anyone opens up.

A leak in your own pipework is normally yours.

Shared risers and communal pipework sit with the freeholder or managing agent.

That usually means a leak on your supply pipe, which is the owner’s responsibility.

Their monitoring flags that a leak exists but not exactly where.

Often, the leak is on the underground run across a front garden.

Once confirmed, you have a legal duty to repair it within four weeks.

Accurate detection first is the sensible step.

Thames Water — leaks and pipe responsibility

Possibly.

Parts of the Eltham area sit within the River Quaggy flood-warning area.

Recurring water after heavy rain may be surface water or groundwater rather than a pipe.

A good plumber checks whether the source is a pipe at all before recommending a repair.

GOV.UK — check long-term flood risk

Some home insurance policies include a trace-and-access clause.

That may cover the cost of finding a leak and making good afterwards.

Check your policy before commissioning work.

Ask the plumber for a written leak-location report with photos and moisture readings for the insurer.

Yes.

Report it in writing.

Royal Greenwich says serious hazards can be reported to its Residential Services team.

The council can step in where a landlord doesn’t act.

Why directory-listed plumbers

Leak detection is a job you’re trusting on the strength of a diagnosis you can’t see for yourself, so who does it matters. Every plumber in our directory has been checked for identity, insurance, trading presence and Gas Safe registration where relevant before listing, and re-checked annually. Listing checks are administrative only — they don’t guarantee workmanship or ongoing compliance, and we are not a regulator; they don’t replace your own checks on the day. For water-fittings and supply work you can look a plumber up yourself on WaterSafe, the free, water-industry-backed national register, and where a job touches gas we confirm Gas Safe registration. Some plumbers offer workmanship guarantees of 3, 6 or 12 months (look for the badge) — set by the plumber, varying in scope, not insurance-backed unless stated, with your Consumer Rights Act 2015 rights still applying. All enquiries go directly to the plumber — no per-enquiry fee, no pay-to-play ranking. See the full verification process →.

Leak detection across Eltham — areas we cover

Verified leak-detection plumbers across Eltham and the wider SE9 area, including the town centre, Well Hall and the Progress Estate, Eltham Park, Eltham Green, Mottingham, New Eltham and Avery Hill.

All plumbers in Eltham · All plumbers in Greenwich

Related services

Burst Pipes · Emergency Plumber · Blocked Drains · Central Heating Repair · Bathroom Plumbing · Tap Repair & Installation

A hidden leak in Eltham is a diagnosis first and a repair second: the value is in locating it precisely, so as little of an interwar or period home is opened up as possible. Trace it, confirm it’s a pipe and not a flood, establish who’s responsible, then repair small.

Contact verified plumbers in Eltham ↑

← Back to all plumbing services in Eltham

Source provenance

Guidance on this page is drawn from primary UK sources: Thames Water (the supply pipe from the boundary is the owner’s; a confirmed leak must be repaired within four weeks; all the water in its region is hard; homes before 1970 may have lead pipes), the Environment Agency and Royal Borough of Greenwich (the River Quaggy flood-warning area and Quaggy-corridor / surface-water risk; council repair and private-tenant routing; Eltham conservation areas). Cost figures are an editorial estimate only. Eltham housing-stock observations are local editorial context, not official data.

Sources & further reading

Thames Water — Pipe responsibility (supply pipe is the owner’s; leak notifications; four-week repair duty; lead pipes) — https://www.thameswater.co.uk/help/water-and-waste-help/leaks/pipe-responsibility
Thames Water — Hard water (“all the water in our region is hard, because it passes through chalky limestone”) — https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
Environment Agency / GOV.UK — River Quaggy at Chinbrook, Mottingham and Eltham flood warning area — https://check-for-flooding.service.gov.uk/target-area/064FWF43Chnbrook
Royal Borough of Greenwich — Level 1 Strategic Flood Risk Assessment (Quaggy corridor and surface-water risk) — https://www.royalgreenwich.gov.uk/download/downloads/id/5792/strategic_flood_risk_assessment_-_level_1.pdf
GOV.UK — Check the long-term flood risk for an area in England — https://www.gov.uk/check-long-term-flood-risk
Royal Borough of Greenwich — Maps and adopted character appraisals (Eltham Palace 1971, Eltham Green 1975, Progress Estate, Well Hall Pleasaunce 1997) — https://www.royalgreenwich.gov.uk/planning-and-building-control/conservation-and-listed-buildings/maps-and-adopted-character
Royal Borough of Greenwich — Request a repair to your council home (020 8921 8900 / 020 8854 8888) — https://www.royalgreenwich.gov.uk/housing/request-repair/request-repair-your-council-home
Royal Borough of Greenwich — Report a problem with a private rented home (Residential Services 020 8921 8157) — https://www.royalgreenwich.gov.uk/housing/request-repair/report-problem-private-rented-home
WaterSafe — Hiring a plumber / verifying qualifications — https://www.watersafe.org.uk/advice/hiring_a_plumber/verifying_qualifications/
Gas Safe Register — Find and check an engineer — https://www.gassaferegister.co.uk/find-an-engineer-or-check-the-register/
London City Hall — Ultra Low Emission Zone (£12.50 daily charge; all London boroughs) — https://www.london.gov.uk/programmes-strategies/environment-and-climate-change/pollution-and-air-quality/ultra-low-emission-zone-ulez-london

Last reviewed: July 2026 by Adiel Khan — SFEDI-accredited business advisor, 20+ years’ experience (South East Enterprise Ltd) and operator of Verified Plumbers. LinkedIn ↗ This page is checked for compliance and regulatory accuracy against Thames Water, the Environment Agency, Royal Borough of Greenwich, WaterSafe and Gas Safe Register guidance. Source links are provided within this page where relevant.

Leak Detection in Eltham