How to tell you have a water leak: checks to make before you call anyone
Practical steps, from reading the damp patch to running a meter test, that tell you whether a leak exists and narrow down where it starts.
Reading the symptom correctly
Water does not show where it escapes; it travels to the easiest route down. A ceiling stain or blistering at skirting level is therefore rarely directly beneath the leak. A sharp, dark edge usually means water is arriving continuously, while a soft, pale edge points to repeated wetting that has since dried. Blistered paint, chalky plaster, darkened tile grout and a wall that feels cold to the touch should be read together, not separately. Draw the outline of the patch in pencil and write the date beside it, and within a few days you will know whether it is still growing.
The water meter test
The simplest way to prove a leak exists is the meter. Close every tap, stop the washing machine and dishwasher, make sure nobody is drawing water, and note all the figures including the fine dial. Repeat the reading an hour later: if the value has moved, water is escaping somewhere beyond the meter. Then close the main stopcock at the apartment entrance and repeat the test; if the meter still turns, the leak is between the stopcock and the meter, and if it stops, the leak is inside the flat. Those two readings halve the search area before anyone starts looking.
Sound, temperature and cistern checks
When the home is quiet, ideally at night, put your ear close to the wall the risers run behind. A pressurised leak gives a thin, steady hiss, while water simply running away sounds duller and lower. In a flat with underfloor heating or a hot water run, an unexplained warm spot in the floor is another sign worth noting. Cistern valves are often missed because they leak silently; a thin, permanent wet trail on the inside of the pan below the water line means the cistern is passing water. None of this is a diagnosis on its own, but it tells the team which line to suspect first.
What to gather before you call
The most valuable thing in a leak request is context, not photographs. Note when the damp becomes obvious: after a shower, after rain, or steadily regardless of use. Find out whether the flat above has had recent work, which wall the neighbour bathroom sits against, and where the building risers run. Share both meter readings, the pencilled outline of the patch and the point where you heard a noise, in writing. Better information means a smaller opening has to be made, which reduces both the repair itself and the surface restoration afterwards.
What not to do
Painting or covering a wet surface hides the problem instead of solving it; the paint will not hold and the stain returns in the same shape. Do not open the wall at random in search of the leak: the wrong spot means unnecessary making good and a real risk of damaging pipework. If water is coming through a ceiling, stop using the lights and sockets in that area, do not touch a wet fitting, and switch off the relevant breaker at the consumer unit; wherever water and electricity meet, isolate the circuit first. Repeatedly pouring chemical drain openers can attack the joints of older pipework. If you are leaving the flat while a leak is active, leave the apartment stopcock closed.
