A leak in the bathroom: is it the pipe, or the grout?
The bathroom is the most common place for damp to travel to the neighbours from — and the most common misunderstanding during a repair. From the outside the two main scenarios look identical: a dark patch on the ceiling below, or a damp wall in the next room. The cause, however, may be a damaged pipe under the screed or simply failed grout and silicone, and the difference in the cost of the repair is tenfold.
How each problem behaves
A leak from a pipe under pressure
Water escapes constantly, whether or not the bathroom is used. The patch grows on days when nobody is at home. The meter turns with the taps closed. The damp is often warm, if the pipe belongs to the hot installation.
A leak through grout, silicone or waterproofing
The damp appears only after bathing and eases if the bathroom goes unused for a few days. The meter stays still. The patch is diffuse rather than sharply defined.
One rule saves a great deal: if the patch grows while you are away on holiday, the problem is a pipe. If it does not, the problem is the waterproofing.
Why the eye is not enough
Both cases produce the same wet patch, and nothing is visible under the tiles. So we rely on measurement rather than assumption:
- A Tramex moisture meter shows the moisture profile at depth. Surface moisture from condensation looks entirely different from screed saturated above a fractured pipe.
- A FLIR thermal camera outlines the shape of the wet zone. A leak under pressure gives a characteristic patch along the run of the pipe; a waterproofing problem gives a spread zone around the wet room.
- Water-load testing — we introduce water into a specific zone under control and watch the response. That separates the trap, the shower tray and the pipework from one another.
What to do before our visit
- Do not wet the bathroom for two hours beforehand. Surface water distorts the moisture meter’s readings.
- Do not heat or cool the room artificially — the thermal camera reads temperature differences and needs a settled state.
- Arrange access to the neighbour below if the patch is at their end. Measuring from both sides halves the time.
- Do not start breaking open. Broken screed makes diagnosis harder, not easier.
And afterwards?
After the measurement you receive a report with the exact location and the nature of the problem. If it turns out to be grout, the repair is cosmetic and cheap. If it is a pipe, you break open exactly where you must, rather than the whole bathroom.
See more about detecting hidden leaks without breaking open, or book an inspection.