The count
| What reaching the fault required | Investigations |
|---|
| Cutting into a floor, wall, ceiling or tiling, or excavating | 8 |
| Nothing opened. The fault was at an accessible fitting or surface | 9 |
| Nothing to repair, because no leak was found in the pipework | 6 |
| Still open at the cut-off date | 2 |
| Total | 25 |
Four of the eight were completed within the period; the other four were specified in the report as the required works and had not been carried out by 18 September 2026. We have counted "required or specified as required" as one category, because the engineering judgement is the same either way.
The eight
- A wall, then a ceiling. Water was gushing through a bathroom ceiling around a light fitting. The rooms immediately above contained no plumbing. A section of wall was opened to trace the pipe run, then the affected ceiling was opened, exposing a pinhole in a 15mm plastic pipe inside the ceiling void, discharging under pressure. Cut out, replaced with a plastic-to-copper connection, pressure tested.
- One floorboard. A heating system kept losing pressure. Tracer gas gave a strong reading in a cupboard under the stairs. A washing machine was moved, one floorboard lifted, and a 22mm heating pipe was there with gnaw marks and a perforation through it.
- A floor in two places. Roughly seven litres a minute lost. Described in full below.
- A toilet removed and a floorboard lifted. Specified, not yet done. Very small pinholes in both the concealed hot and cold pipework between a bath and a toilet, too small to pinpoint individually, so the recommendation was to replace the sections rather than hunt for each hole.
- Buried pipework exposed below a hall floor. Specified. A joint between old imperial-sized plastic pipe and a stopcock, confirmed visually under pressure after tracer gas located it. The report also specified retaining a physical sample of the old pipe, because imperial sizing cannot be assumed at a merchant's counter.
- An external soil stack cut out from a tower. Specified. A hole at a 45-degree junction on a four-inch soil pipe, which only discharged into the brickwork when the bathroom above was used.
- Bathroom tiles removed. Specified. A bath waste pipe had come off its brackets, opening the joint every time the bath drained. Water had penetrated the bedding mortar under intact tiles, so the tiles had to come up to reach the pipe.
- The ground excavated. Specified. A buried incoming supply pipe roughly a metre down, proven by isolating every internal stopcock and watching the external meter keep running, but not pinpointed because neither water nor tracer gas surfaced at that depth.
Six of the eight were under a floor or in the ground. Only two were in a wall or ceiling. If you are bracing for damage, the floor is the likelier casualty.
The job where the first opening was wrong
This one is the reason we will not tell you tracer gas puts a cross on a floorboard.
A property was losing about seven litres a minute. A minor drip at a kitchen tap was found immediately and recorded as far too small to explain it. The system was drained, tracer gas introduced, the outside checked with nothing found, and the inside surveyed. A strong, sustained reading came up in a reception room near a doorway, and the floor there had visibly sunk relative to the rest of the room.
A section of floorboards was cut and lifted at that point. There was no pipework underneath. A telescopic camera went into the void and found none either.
So the gas was introduced again and the survey repeated. This time it led towards the void beneath a staircase, where escaping water could also be heard. A screwed-down panel came up and a lead supply pipe with a hole in it was there. Reaching it needed two further sections of hall flooring cut out. Heating pipes and hot and cold water pipes ran directly above the failed lead pipe, and taking them out to get a clean cut-and-replace would have meant substantially more damage for no better outcome, so a repair clamp was fitted over the hole. The external meter then showed no usage, the system held under a pressure test, and both areas of flooring were reinstated.
Three openings, one of them in the wrong place, and a repair method chosen for how little else it destroyed. That is what this work actually looks like.
The nine where nothing was opened
It is worth being equally specific about the other side, because it is the larger group. In nine of the twenty-five, the fault was reached without cutting into anything:
- A loft tank ball valve and a WC filling valve, both passing, replaced.
- Two WC cisterns and a bath tap.
- A shower waste connection resealed and the tray silicone renewed.
- A bath tap with a failed diverter, replaced.
- Missing grout on the bottom row of shower tiles.
- A ball valve seized with limescale, freed and cleared.
- An elbow on a toilet supply, reached and repaired.
- A blocked gully outside, cleared.
- A failed cold supply behind a toilet, reached by taking down an existing access board. No structure was cut, and nothing needed making good.
That last one is the argument for access panels. The same fault, in the same position, in a property without a panel, is a tiled boxing that has to be destroyed. One of the reports in this set recommends installing a removable access panel beneath a shower tray specifically so the next inspection does not require demolition, and it is sound advice for any concealed cistern, shower trap or stopcock.
Why the opening is not the expensive part
Lifting a floorboard is cheap. Putting a floor, a ceiling, a tiled wall or a driveway back is not, and this is where most leak jobs in London go wrong commercially.
A detection firm finds the leak and leaves. A plumber repairs the pipe and leaves. The hole, the lifted screed, the cut ceiling and the missing tiles are then somebody else's problem, usually the owner's, usually arranged over several weeks with two more trades. That gap is the reason this firm exists: we carry our own handymen and builders, so the flooring, screed, plaster, ceiling, tiling and decoration are part of the same job rather than the next three.
It is also the reason to understand your policy before the work starts. Most buildings insurance in the UK covers trace and access, meaning the cost of getting to the leak and making good afterwards, even where the damaged pipe itself is excluded. What that cover is and what it does not pay for are both worth reading before anyone cuts anything, because the sequence of events affects what you can claim.
Keeping the opening small
Three of these bookings asked, in writing, for the cut-out to be as small as possible. That is the right instruction and it is achievable, but only in a particular order:
- Pressure test first. Establish that there is a loss and which circuit it is on. In one job, the cold held for 30 minutes and the hot dropped instantly, which halved the search before anything was touched.
- Then locate, then open. Tracer gas gives an area. A camera through a small hole can confirm the exact point inside that area before a larger opening is made. In one job here, a camera through a small access found water escaping beneath a toilet pan connector, and a single access board came off instead of a floor.
- Accept that an area is not a point. As the seven-litre-a-minute job shows, a strong tracer reading can be metres from the pipe on a suspended floor, because the gas travels through the void. Budget for the possibility of a second opening rather than being told it will never happen.
- Repair for access, not for elegance. A clamp on a lead pipe under a floor, with three other services stacked above it, is a better outcome than a textbook cut-and-replace that requires dismantling those services. Ask what the alternative would have cost in damage.
Limits
Twenty-five investigations from one firm's London caseload between 17 July and 18 September 2026, classified by hand. Whether a job "required opening up" involves judgement in borderline cases: we counted an existing access panel as not opening up, and we counted works specified in a report but not yet carried out as requiring it. Four of the eight had been completed by the cut-off and four had not, so this measures what was engineered as necessary rather than what was finished. Twenty-five is small and the mix leans towards tenanted flats and blocks. The full method, universe and exclusions are set out in the dataset post.
