How do you find a leak without ripping the floor up?

By narrowing it before cutting. Pressure testing says which circuit, thermal imaging follows the run, moisture mapping finds the high point of the wet area and tracer gas resolves what is left. The floor is then opened at one located point. Blind searching is what produces the horror stories, and it is avoidable in most properties.

My water bill has jumped but I cannot see any damp. Is that a leak?

Often, yes — an underground supply pipe leak soaks away into the ground and never shows inside the house. Run a meter test with every tap closed. If the dial moves with the internal stopcock shut, the loss is on your buried supply pipe, which is a different job from an internal leak.

Can you find a cold water leak with a thermal camera?

Not reliably. Thermal imaging reads temperature difference, and a cold pipe leaking into a cold floor produces very little of it. That is exactly the case tracer gas exists for, because gas does not care what temperature the pipe is.

Do you repair the pipe on the same visit?

Where the access allows, yes — the engineers carry pipe and fittings, and the repair follows the detection in the same appointment. Excavation for a buried supply pipe and work inside a communal riser are the usual reasons it becomes a second visit.

Who repairs the floor after you have opened it?

We do. Flooring, screed, plaster, ceilings, tiling and decoration are all in-house, so the opening we make is the opening we close. That is not the normal arrangement in this trade, and it is the main reason people come to us instead of a detection-only firm.

Repairs

Water Leak Repair in London

A hidden water leak is located by pressure test, thermal imaging, moisture mapping and tracer gas before anything is opened, then the failed pipework is cut out and replaced and the floor or wall it was buried in is put back — all by the same firm, at £150 per hour agreed in advance.

A Leak Fix London engineer working on pipework in a London home

What the job includes

Meter and stopcock test to place the leak inside or outside the property
Circuit-by-circuit pressure testing to identify the failing run
Thermal imaging and acoustic tracing along the pipe route
Moisture mapping to find the high point of the wet zone
Non-invasive tracer gas where thermal and acoustic cannot resolve it
Pipework repair or section replacement in copper, MDPE, push-fit or lead
Held pressure test before the access is closed
In-house reinstatement of floors, screed, plaster, ceilings, tiling and decoration

No find, no fee · £150 per hour. The rate is fixed before we attend and does not rise for a difficult property, an awkward access or an evening visit. The total depends on how long the job takes; the rate cannot change.

The leak you cannot see is the expensive one

A visible drip gets fixed. The leaks that cost people thousands are the ones with no obvious source: a bill that has doubled, a meter dial that turns with every tap closed, a patch of floor that is always slightly cold, a boiler that needs topping up every fortnight. The pipe has been losing water for months and the damage is in the structure before anyone sees a drop.

Almost every London firm in this market will find that leak for you and then hand you a report. We find it, repair the pipe, and reinstate whatever had to come up to reach it.

How we find it

There are four methods and they answer different questions. A competent visit uses whichever combination the property demands, not whichever one the van happens to carry.

Pressure testing. The first thing we do is prove the loss exists and work out which circuit it is on. Isolating the hot, the cold and the heating in turn and watching a gauge separates three possible jobs in about twenty minutes, with nothing opened up.
Thermal imaging. A hot pipe losing water warms the material around it in a shape a camera can read through screed, tile and plasterboard. It follows the run. It cannot see a cold-water leak that has reached ambient temperature, which is why it is never used alone.
Moisture mapping. A meter across the floor or wall builds a map of the wet zone. Water runs downhill and spreads, so the wettest point is not the leak — the highest point of the wet area is the one that matters, and that is what the mapping finds.
Tracer gas. The pipe is drained and a hydrogen and nitrogen mix is pushed in under pressure. The gas is small enough to escape through the defect and rise through screed, sand, tile grout and floorboards, where a surface probe picks it up. It is non-invasive, it works on cold pipework that thermal cannot see, and it is what resolves the cases where two candidates look equally likely. There is a dedicated page on tracer gas leak detection if you want the detail.

How the visit runs

We walk the property with you and take the history: when it started, what changed, what has already been done. Previous repairs are often where the current leak is.
Meter test with everything closed, if you are metered. A turning dial with the internal stopcock shut puts the leak outside the house on the supply pipe; a dial that stops when the stopcock is closed puts it inside.
Circuits isolated one at a time and pressure-tested to identify the failing one.
The run is traced along its length using thermal, acoustic and moisture readings, and the location is narrowed to a point rather than an area.
Tracer gas is used where that has not resolved it, or where the pipe is cold.
One access opening is made at the located point.
The pipe is repaired, tested at pressure with the opening still visible, and then the opening is closed and made good.

What London housing stock actually throws up

Pipework failure is a function of what was installed, when, and what has been done to it since.

Victorian and Edwardian terraces

Lead supply pipe still running from the boundary under the front path is common, sometimes joined to copper at a transition fitting that has been slowly failing for decades. Inside, 15mm copper is clipped or notched into joists, and where a notch has held damp the outside of the pipe corrodes as well as the inside. Pipework buried in a chased wall under plaster, installed when the bathroom was moved upstairs, is the other regular.

Purpose-built blocks, 1930s to 1970s

Solid concrete floors mean pipework runs in the ceiling void of the flat below or in a boxed vertical duct. Communal risers serve several flats, and a leak in a riser is not a leak in your flat even though your flat is the one getting wet. Establishing that early is the difference between your money and the freeholder's.

Converted flats

Kitchens and bathrooms have been relocated to wherever the conversion put them, so supply and waste cross joists at odd angles and long horizontal runs sit above habitable rooms. Boxed-in stacks and boxed pipe runs hide the evidence until it soaks through.

New builds and refurbishments

Plastic push-fit in floor build-ups and ceiling voids, occasionally without the insert fully seated. Screed floors with underfloor heating absorb a slow loss for months. Manifolds sit in a cupboard where a slow weep runs quietly into the floor.

Basement conversions

Water has nowhere to drain to, tanking makes damp readings harder to interpret, and services enter through the retaining wall. These take longer to diagnose, and it is worth knowing that before the clock starts.

The repair

Once the point is located, the failed section is cut out and a new section goes in — copper soldered or press-fitted, MDPE coupled, push-fit remade correctly, lead replaced rather than patched. Where a run has already failed twice, we will tell you plainly that patching it a third time is throwing money at it and offer to re-run the section instead. See pipework repair and replacement for how that is done.

The repair is then held at working pressure with the access still open, so you can see the joint dry before it disappears behind a floor again.

Making good, in-house

We employ handymen and builders alongside the engineers, so the reinstatement is part of the same job rather than a referral. Floorboards relaid and the covering put back. Screed cut filled, levelled and left ready for tile or engineered board. Chased walls filled, plastered and decorated. Ceilings boarded, skimmed and painted. Tiling cut in and grouted. This is the reason people call us rather than a detection-only firm: the hole in the floor is our responsibility, not yours to solve afterwards.

Things you can check yourself first

Before booking anything, thirty minutes of your own will either narrow it or rule us out.

Meter test. Close every tap, note the meter, wait an hour, read it again. No movement and no visible damp means there is probably nothing to find. There is more on this under water bills and meters.
Stopcock test. If the meter moves, close the internal stopcock and read again. Still moving means the leak is on the buried supply pipe outside.
Rain test. If the damp appears or worsens only after rain, this is not plumbing. That is a roof, a gutter, a window seal or pointing.
Dry and ringed. A hard, dry stain with a sharp tidemark is a historic leak that has stopped. Painting over it before sealing will bleed through; calling a leak engineer will find nothing.

Terms

£150 per hour, fixed before we attend. It does not go up for a difficult property, awkward access or an evening visit. The total depends on hours and materials, which nobody can honestly quote before seeing the job — the rate is what we can fix, and we do. No find, no fee: if we do not locate the leak, you do not pay for the time spent looking. Every job includes a written leak detection report set out to be accepted by an insurer for a trace and access claim.

Frequently asked

How do you find a leak without ripping the floor up?: By narrowing it before cutting. Pressure testing says which circuit, thermal imaging follows the run, moisture mapping finds the high point of the wet area and tracer gas resolves what is left. The floor is then opened at one located point. Blind searching is what produces the horror stories, and it is avoidable in most properties.
My water bill has jumped but I cannot see any damp. Is that a leak?: Often, yes — an underground supply pipe leak soaks away into the ground and never shows inside the house. Run a meter test with every tap closed. If the dial moves with the internal stopcock shut, the loss is on your buried supply pipe, which is a different job from an internal leak.
Can you find a cold water leak with a thermal camera?: Not reliably. Thermal imaging reads temperature difference, and a cold pipe leaking into a cold floor produces very little of it. That is exactly the case tracer gas exists for, because gas does not care what temperature the pipe is.
Do you repair the pipe on the same visit?: Where the access allows, yes — the engineers carry pipe and fittings, and the repair follows the detection in the same appointment. Excavation for a buried supply pipe and work inside a communal riser are the usual reasons it becomes a second visit.
Who repairs the floor after you have opened it?: We do. Flooring, screed, plaster, ceilings, tiling and decoration are all in-house, so the opening we make is the opening we close. That is not the normal arrangement in this trade, and it is the main reason people come to us instead of a detection-only firm.