Damp patches, ceiling stains, a hiss behind the wall and boiler pressure that won't hold — how to narrow down a hidden leak in a Coleraine home, honestly.
A hidden leak usually announces itself sideways: a damp patch that keeps returning, a ceiling stain that grows, a musty smell, the faint hiss of running water when everything is off, or boiler pressure that keeps dropping. The quickest way to narrow it down is the stopcock test — everything off, stopcock closed, then watch and listen. If water is anywhere near electrics or a ceiling is sagging, skip the detective work and call now.
Hidden leaks rarely make a scene. They show up as a damp patch on a wall or floor that dries out and comes back, a ceiling stain with an edge that creeps outward, a musty smell that lingers in one room however often you air it, or the faint hiss of running water when every tap and appliance is off. Boiler pressure that needs topping up again and again belongs on the same list — a sealed heating system only loses pressure by losing water.
Most homes in Northern Ireland are unmetered, so a surprise bill won't warn you the way it might elsewhere. But if your home has a water meter, a reading that keeps climbing while nothing is running is telling you the same story. Some of the older housing stock around Coleraine runs pipework through voids under floors and behind solid walls, which is exactly where a small leak can weep for months unseen.
It's the honest, low-tech way to narrow things down. Turn off every tap and everything that uses water — washing machine, dishwasher, any softener — then close the stopcock. Now watch and listen. If the damp patch stops growing, or the hiss goes quiet, the leak is on your own pipework, somewhere after the stopcock: that's a job for a plumber with the right tools to trace it. If nothing changes with the stopcock shut, the moisture may not be a supply leak at all — think drains, rainwater or condensation — which is genuinely useful to know before anyone lifts a floorboard.
If your home has a water meter, add the second version: read it, use no water at all for 30 to 60 minutes, then read it again. Any movement on the dial means water is escaping somewhere between the meter and your taps.
Because the heating circuit is its own sealed loop, a leak there often never shows as a puddle: a weeping radiator valve, a pinhole in a pipe under the floor, or a fault inside the boiler itself can all bleed the system slowly. If you're topping up every week, treat that as a hidden leak with a gauge attached — repeated topping up hides the symptom without fixing the cause. Tell the plumber how often you top up and by how much; it genuinely helps the diagnosis.
Damp patches that keep coming back, ceiling stains that slowly grow, a musty smell in one room, the faint hiss of running water when everything is off, or boiler pressure that keeps dropping. Most homes in Northern Ireland are unmetered, but if your home has a water meter, a reading that keeps climbing while nothing is running is another clue.
Turn off every tap and appliance that uses water, then close the stopcock. If a damp patch stops growing or the hiss goes quiet, the leak is on your own pipework — a job for a plumber. If your home has a water meter, read it, use no water for 30 to 60 minutes, then read it again: any movement means water is escaping somewhere.
When water is anywhere near sockets, switches or the fuse box, when a ceiling is sagging or bulging, or when a damp patch is visibly spreading while you watch. Shut the stopcock, keep people from under a bulging ceiling, and call straight away rather than waiting for a convenient moment.
Yes. A sealed heating system that needs topping up again and again is losing water somewhere — often a weeping joint or a small leak under floors that never shows itself as a puddle. Repeated topping up hides the symptom without fixing the cause, so it's worth getting the leak traced rather than living with the ritual.
Yes. Most homes in Northern Ireland are unmetered, so the version to use is the stopcock one: everything off, stopcock closed, then watch and listen. If the patch stops growing or the hiss stops while the stopcock is shut, the leak is on your side of the supply, and a plumber can trace it from there.
Back to the Coleraine emergency plumber home page, or jump to another guide:
Stopcock first: the three steps that limit water damage fast.
Read the guide →Pressure basics, no heat or hot water, and what to do about a gas smell.
Read the guide →What never to pour away, and when a blockage is a main-drain problem.
Read the guide →An honest look at call-out fees, hourly rates and out-of-hours pricing.
Read the guide →Pressure, thermostat, tripped switch or diverter valve — checks first.
Read the guide →Stopping pipes freezing in the first place, and thawing one safely.
Read the guide →The main page: what to do right now and the areas covered.
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