Leak Detection in London: Finding Water Without Opening Walls

Rillwater Plumbing & Heating traces hidden water leaks across sixteen London boroughs using thermal imaging, acoustic correlation and tracer gas, so the source is found before a floor or a wall is opened. You get the position marked and photographed, a written report your insurer can use, and a repair price. Book a leak survey here, or call 07446 375079.

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Directly employed engineers, not subcontractors
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Tell us the fault and your postcode. We reply with a time and a price before anyone travels.

How is a hidden leak found?

Four methods locate a leak without opening the building: thermal imaging, acoustic correlation, tracer gas and moisture metering. Thermal imaging reads temperature difference through plaster and screed. Acoustic correlation places the escape between two listening points. Tracer gas suits plastic pipe and drained circuits.

A water leak is water escaping a pressurised supply or a heating circuit at a point not intended to discharge. The method is chosen by pipe material and by construction, never applied as a bundle. Metal pipe transmits the sound of an escape along its length, which is what a correlator exploits. Plastic pipe damps that sound within a few metres, which is why a plastic run is drained and charged with gas instead. A screed-embedded circuit carries warm water, which is what a thermal camera sees.

Four detection methods, what each measures, and the situation it belongs to.
Method	What it measures	Used on
Thermal imaging	Surface temperature difference through plaster, tile and screed	Underfloor heating circuits, heating pipework in floors and walls, hot supply runs
Acoustic correlation	Arrival time of the escape sound at two sensors on the same pipe	Buried metal supply pipe between the boundary stopcock and the property
Tracer gas	Hydrogen surfacing through a floor, a wall or the ground above the escape	Plastic pipe, drained circuits, and any run too quiet to correlate
Moisture metering	Moisture content of the material itself	Bounding the wet area before the other three narrow it to a point

Tracer gas is a hydrogen and nitrogen mixture introduced into a pipe that has been drained first. Hydrogen is the smallest molecule available, so it travels out through the fault and up through screed, tile or soil, and a surface detector reads it where it emerges. Moisture metering bounds the wet area rather than fixing the point, which is why it runs first and never alone.

How do I know I have a leak at all?

Six signs point to a hidden leak: a rising water bill, a meter that turns with every tap closed, a warm patch on a floor, a damp patch spreading on a ceiling, a boiler losing pressure, and a musty smell with no visible source. Any one justifies a survey.

A rising water bill with no change in occupancy or habit. The volume is going somewhere, and a meter reads it whether or not the water reaches a tap.
A meter that turns with every tap closed. Close the internal stopcock and the meter stops if the escape is inside; it keeps turning if the escape is on the buried supply pipe outside.
A warm patch on a floor. Warm water escaping into screed heats the surface above it, and the patch sits over the pipe rather than over the room’s radiator.
A damp patch spreading on a ceiling. Water tracks along a joist before it drops, so the stain marks where the water fell, not where it left the pipe.
A boiler losing pressure. A sealed heating system holds a fixed volume of water. A gauge falling week on week proves that volume is escaping somewhere on the wet side.
A musty smell with no visible source. Persistent moisture inside a floor void or a stud wall produces odour long before it produces a stain.

What does leak detection cost in London?

A leak detection survey is quoted as a fixed fee, and that fee is stated before the appointment is booked. The survey produces a marked and photographed position plus a written repair price. Access difficulty and property size change the figure, and both are established on the phone beforehand.

Two variables move the fee and neither is discovered on the day. Floor area sets how much surface has to be read, and a whole ground floor takes longer than a single bathroom. Access sets whether the pipe can be reached at all: a boxed riser, a fitted kitchen or a communal cupboard with a managing agent’s lock each add time before any reading is taken.

⚠ No survey fee is published on this page. Rillwater has invoiced no survey yet, and a figure lifted from another firm’s price list is that firm’s figure. The fee is quoted on the call, in full, before the appointment is confirmed.

How long does a leak survey take?

A domestic leak survey takes two to four hours. A single-fault supply leak in an accessible flat sits at the lower end. A screed-embedded underfloor heating circuit across a whole ground floor sits at the upper end, because the floor must reach a stable temperature before it is read.

Thermal imaging depends on a temperature difference existing at the moment of the reading. A screed floor holds heat for hours, so the circuit is run up and then allowed to settle before the camera is used, and that settling period is most of the difference between a two-hour visit and a four-hour one. The report follows the same day, carrying the marked position, the photographs, the method that found it and the price to repair it.

Surveys are attended in Barnet, Bromley, Camden, Croydon, Ealing, Greenwich, Hackney, Hammersmith and Fulham, Islington, Kensington and Chelsea, Lambeth, Lewisham, Southwark, Tower Hamlets, Wandsworth and Westminster. Sixteen boroughs, one directly employed team, and the same equipment on every visit.

Finding the water answers one question. Who pays to put it right is a different one, and it turns on where the leak sits relative to a valve buried at the front of the property.

Whose pipe is it — mine or the water company’s?

The boundary stopcock is the dividing line. The communication pipe, running from the water main to the boundary stopcock, belongs to the water company and is repaired at their cost. The supply pipe, running from that stopcock into the property, belongs to the property owner.

Ownership does not follow the garden wall, which is what most householders assume. The supply pipe stays the owner’s responsibility along its whole buried length, including any part crossing a pavement, a shared drive or a neighbour’s ground. A leak two metres inside the boundary and a leak twenty metres away under a private road are both the owner’s, and both are found by the same correlator.

The test that separates the two is quick. Close the internal stopcock and watch the meter. A meter still turning means water is escaping between the boundary and the house, on the owner’s supply pipe. A meter that stops means the escape is inside the building. Water surfacing in the public footway, with the boundary chamber running, points at the company’s communication pipe, and that repair is theirs at no charge.

Will my insurance pay for the search?

Most household policies cover escape of water, and many carry a separate trace and access clause paying to find the leak and reinstate what was opened up. The survey report, the marked position and the photographs are the evidence an insurer asks for. Check the clause before booking.

Escape of water is the insurance category for sudden damage from a burst or leaking pipe. Trace and access is a distinct clause with its own limit, written into the policy schedule as a figure per claim, and it pays for the investigation and the making good rather than for the damage. The two are frequently confused, and the confusion costs money in exactly one direction.

Insurers ask for the same four things: the date the escape was discovered, photographs taken before anything was moved, a report naming the position and the method that located it, and a quotation for the repair. A non-invasive survey supplies three of the four in one visit, which is why it is booked before a floor is lifted rather than after.