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The signs you have a hidden leak in your Bexley property

Some leaks announce themselves. Most don’t. These are the signs to act on before the damage becomes serious.

Unexplained rise in your water bill. If your usage has gone up and nothing in the house has changed, water is escaping somewhere. Check your water meter — turn off everything in the property and watch the meter for 30 minutes. If it moves, you have a leak.

Taking a short video of the meter moving while all taps are off is a useful record to have if you later make an insurance claim.

Boiler losing pressure repeatedly. In a sealed central heating system, pressure that drops regularly means water is escaping the circuit. This is one of the most common hidden leak presentations in Bexley’s inter-war housing stock, where original pipework under floors or behind walls can fail without any visible sign at the surface.

Damp patches on walls, ceilings or floors. A damp patch that grows, reappears after drying, or appears without obvious cause. In inter-war Bexley semis, damp on ground floor walls near the front of the house often points to a supply pipe failure under the path or driveway.

Musty smell in a specific area. Persistent musty odour in one room or cupboard — especially under stairs or near the airing cupboard — often signals a slow leak that has been present long enough to encourage mould behind the surface.

Sound of running water when everything is off. If you can hear water movement inside walls or under floors with no appliance running, treat it as a confirmed leak until proven otherwise.

Cold spots on previously warm floors. In properties with underfloor heating, a cold patch in a previously warm area of floor is a reliable indicator of a circuit leak at that point.

How leak detection works — what the engineer does

A professional leak detection survey does not start with a hammer and a crowbar. It starts with diagnostics.

Acoustic detection uses sensitive listening equipment to pick up the sound frequencies of pressurised water escaping through a pipe.

The engineer works systematically across floors, walls and ceilings, listening through surfaces. In Bexley’s inter-war semis with original suspended timber floors, acoustic detection can locate a pinhole leak under the floorboards without lifting a single board.

Thermal imaging scans surfaces for temperature anomalies caused by moisture. Hot water leaks warm surrounding materials; cold water leaks cool them. A thermal camera shows where a leak has been long enough to affect the temperature of the structure around it.

This is particularly effective in Bexley’s Victorian terraces in Erith and Belvedere, where pipes run through thick walls that would otherwise require extensive opening up.

Tracer gas testing introduces a safe, inert gas into the pipework. The gas rises through any building material and is detected at the surface by a sensitive probe, pinpointing the exact leak location. This method works on underground supply pipes, concrete slabs and any situation where acoustic and thermal imaging produce inconclusive results.

Moisture meters measure the moisture content of walls, floors and ceilings. They confirm whether a suspect area is actively wet, drying out, or dry — telling the engineer how long a leak has been present and how far the water has travelled.

A competent leak detection engineer uses these methods in combination, working from least invasive to most, and does not start accessing structure until the leak location is confirmed.

Inter-war semis — the specific leak risks in Bexley

Bexley Council’s Local Plan (Adopted 2023) describes the borough as characterised by predominately privately owned, inter-war, low-density residential neighbourhoods.¹

Inter-war semis in Bexleyheath, Sidcup, Welling and Barnehurst carry specific leak risk profiles that differ from newer housing.

Original lead or early copper supply pipes. Pre-war and early post-war supply pipework is prone to pinhole corrosion over time. Hard water contributes to scale buildup and long-term wear in pipework and components. A slow drip from a pinhole under the front path can go undetected for months.

Compression joints under floors. Inter-war semis frequently have original compression joints on copper runs under suspended timber ground floors. These joints were well-made, but decades of thermal movement and vibration loosen them. A joint that was dry last year can start weeping this year with no other trigger.

Gravity-fed systems and cylinder connections. Properties still running on open-vented systems have a hot water cylinder with multiple pipe connections — cold feed, primary flow and return, vent pipe. Any of these connections can develop a slow weep inside the airing cupboard. Because the cupboard itself absorbs moisture, the leak is often masked until the structural timber is already affected.

Scale and hard water. In Bexley postcodes that show very hard results in the Thames Water postcode checker, scale buildup contributes to long-term wear on pipework and components.² Always tell the engineer your hard water level — it changes where they look first.

Victorian and Edwardian stock — Erith, Belvedere and Crayford

Victorian terraces in Erith DA8, Belvedere DA17 and Crayford DA1 present a specific leak challenge: shared supply pipes and thick masonry walls that conceal leaks for longer.

Shared supply pipes. Thames Water confirms that some properties share a supply pipe with neighbours.³ A leak on a shared section may present in one property while originating in a shared run.

Checking with your neighbours whether they have also noticed rising bills or reduced pressure is a useful supporting step — Thames Water will confirm responsibility if you report the issue to them directly.

Thick Victorian masonry. Walls up to 225mm thick in solid brick construction absorb and distribute moisture much further from the source than modern cavity wall construction.

A leak behind a Victorian wall in Erith can show as damp several metres from the actual failure point. Thermal imaging is particularly valuable in this stock — it maps the moisture distribution pattern, helping the engineer trace back to the source.

Lead pipework. Pre-1970 properties in Erith and Belvedere may still have lead supply runs. Lead pipes can develop hairline splits that weep slowly without dramatic pressure loss. Thames Water’s Customer Side Lead Pipe Replacement scheme covers replacement of the communication pipe once the homeowner replaces their supply side.⁴

Your responsibility and Thames Water’s — getting it clear before you spend money

Thames Water is clear on the division of responsibility:⁵

Your responsibility: The supply pipe from your property boundary into the house, and all internal pipework, fittings and appliances.

Thames Water’s responsibility: The water main under the road and the communication pipe to your boundary.

Thames Water advises that leaks on your property should be repaired promptly once identified.⁵ If the leak is on Thames Water’s network — in the road or pavement — call them on 0800 316 9800, not a leak detection engineer.

If you are a tenant, Thames Water confirms your landlord is responsible for fixing leaks.³ Report in writing and keep a copy. Your landlord’s repair obligation sits under Section 11 of the Landlord and Tenant Act 1985.⁶ If the landlord fails to act, contact Bexley Council’s housing team.⁷

Trace and access — using your home insurance

Most standard home insurance policies include a trace and access section under the escape of water cover. Trace and access pays for the cost of locating the leak and accessing it — the investigation and any necessary opening up of structure. Cover is often capped around £5,000 depending on the policy, though some policies use a reasonable cost model.

For older Victorian properties in Erith and Belvedere where thick masonry may require more access work, it is worth checking whether your policy has a per-claim or per-annum limit before instructing work — costs in older Bexley stock can occasionally exceed standard limits.

Check the escape of water section of your policy before commissioning a survey. If you are covered, contact your insurer first — they may direct you to an approved contractor or require a written quotation before work begins. A professional leak detection report with photographs is commonly requested by insurers to validate a trace and access claim.

Trace and access cover pays for locating and accessing the leak. The repair itself is usually classified separately under escape of water damage cover. Get clarity on both sections before instructing work.

What to tell the leak detection engineer before they arrive

The more information you can give upfront, the more efficiently the survey runs. Tell them:

• Property type and approximate age — 1930s semi, Victorian terrace, purpose-built flat
• Where you have noticed damp, sounds or pressure loss — be as specific as possible
• Whether the issue is on the heating circuit, the cold supply, or hot water
• Whether the boiler is losing pressure and at what rate
• Whether your water meter has been checked and showed movement — and whether you have a video record
• Any recent pipework work that might be relevant

What leak detection costs in Bexley — 2026

Editorial estimate — not an official council, utility or government price source. These ranges reflect typical London market rates and are a guide only. Prices current as of April 2026. Always obtain a written quote before work begins.

Leak detection surveys are priced per investigation, not per hour. Get a clear written quote specifying what methods will be used and whether a written insurance report is included.

Frequently asked questions — Leak Detection Bexley

Sources & further reading

¹ London Borough of Bexley — Local Plan (Adopted 2023)
² Thames Water — Hard water classification and postcode checker
³ Thames Water — Pipe responsibility
⁴ Thames Water — Customer Side Lead Pipe Replacement scheme
⁵ Thames Water — Leaks at home
⁶ UK Legislation — Landlord and Tenant Act 1985, Section 11
⁷ London Borough of Bexley — Property disrepair including damp and mould