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The most expensive leaks are the quiet ones — working behind a wall for months while everyone blames the weather. Here's what a hidden leak actually looks like, the one test that costs nothing, and the moments when watching becomes calling.
Suspect a hidden leak right now? Turn off every tap and appliance, then close the stopcock: if a damp patch stops growing or a hissing sound stops, the leak is on your own pipework. If water is near electrics or a ceiling is bulging, keep clear and call 020 4577 2888 to be connected with a local plumber, any hour.
Rarely like a leak. The classic evidence list: a damp patch that returns however often it dries, a tea-coloured stain spreading on a ceiling, paint or wallpaper lifting, a musty smell in one particular corner, a faint hiss of running water when the house is silent, and a boiler that keeps needing its pressure topped up. In Portadown's older red-brick terraces, where pipework from several eras runs under floors and through solid walls, a slow weep can work unseen for a long time — the house usually mentions it before the pipe does.
MythNo puddle, no leak — damp patches are just condensation.
FactCondensation is real, but it has habits: it favours cold surfaces, windows and unventilated corners, and it eases when you air the room. A leak doesn't care about ventilation. A patch that keeps its shape, keeps its place and keeps coming back — especially below a bathroom or along a pipe run — has earned proper suspicion, not another run of the dehumidifier.
Almost embarrassingly. Turn off every tap and water-using appliance, then close the main stopcock. Now watch and listen: if the hiss stops, or a growing damp patch quietly gives up, the water feeding it was yours — the leak is on your side of the boundary, somewhere on your own pipework. If your home has a water meter — most homes in Northern Ireland don't, so no guilt if you've never seen one — there's a more precise version: read the meter, use no water at all for 30 to 60 minutes, and read it again. Movement on the dial with everything off is water escaping somewhere.
One honest caveat: the test tells you a leak exists and whose it is, not where it hides. Finding it is the trade's job — often the biggest part of the job.
MythA leak under the floor will make itself known soon enough — wait for proof.
FactBy the time a slow leak produces courtroom-grade proof, it has usually rotted a joist, saturated insulation or brought a ceiling down for emphasis. Water damage is priced by duration. The evidence you already have — the stain, the smell, the pressure that keeps dropping — is the cheap version of the proof that arrives later.
Most hidden leaks allow you a considered response. Three do not:
In each case: stopcock off, electrics respected, phone next. Everything else on this page can wait for daylight; these three can't.
A sealed heating system that needs topping up again and again is leaking, somewhere between the boiler and the furthest radiator — sometimes into a floor or wall where nothing shows for months. Repeated top-ups treat the gauge, not the fault. That pattern is a hidden leak announcing itself, and it deserves tracing rather than another squirt of the filling loop.
The boundary decides it. Broadly, the supply pipe from the property boundary into your home is the owner's responsibility; leaks on the public side — the mains — are a matter for NI Water in Northern Ireland. Shut your stopcock: if the leak or damp patch stops responding, it's on your side. Water bubbling up in the street or verge points the other way.
It's evidence of persistent damp, and a slow hidden leak is one of the commonest causes. A musty corner, lifting paint, a skirting board going soft or mould that keeps returning after cleaning all say the same thing: moisture is arriving faster than it can dry. The smell won't tell you which pipe — but it tells you to start looking.
Three situations end the watching-and-waiting: water anywhere near sockets, light fittings or the consumer unit; a ceiling that is sagging or bulging; and a damp patch that is visibly spreading while you watch. In any of those, shut the stopcock, keep clear of the electrics and the plaster, and call straight away — those are same-hour problems.
If the signs are growing and nobody can look at it until morning, closing the stopcock overnight is a sensible, free precaution — a slow leak can't do much with no supply feeding it. Fill the kettle and a couple of pans first, and mention what you did and what changed when you call: it's genuinely useful diagnostic information.
The main page — how the line works, areas covered, and the big myths.
Go to home →Stopcock first, towels later — and whose pipe it is when the leak is outside.
Read the guide →Pressure, lockouts, noises — and the gas rule that has no exceptions.
Read the guide →What clears a blockage, what builds one, and whose drain it is.
Read the guide →Pressure, timers, tripped switches and the diverter-valve giveaway.
Read the guide →Gentle heat from the tap end, never a flame — and the lagging that prevents it all.
Read the guide →Hedged national ballparks and the questions to ask before work starts.
Read the guide →Any hour, any day — be connected with a local plumber covering Portadown, Craigavon, Lurgan and the surrounding County Armagh area.
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