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The leaks that cost the most never show up on a forecast at all. Here's how to read the clues, run one honest test, and know when it can't wait.
Think there's a leak you can't see? Turn off every tap and water-using appliance, then close the stopcock and watch the evidence: if the damp patch stops growing or the hiss goes quiet, the leak is on your own pipework. Water near electrics, or a sagging ceiling? Don't wait for tests — ring 020 4577 2888 now to be put through to a local plumber, any hour.
Your house tells you sideways: damp patches, ceiling stains, a musty smell, a faint hiss, a boiler gauge that keeps falling. Any one alone is a maybe — two together deserve action.
Hidden leaks rarely announce themselves directly. A damp patch on a wall or chimney breast that comes back after you dry it. A tea-coloured ring on a ceiling under the bathroom. A musty smell in one room that nothing else explains. Flooring that lifts, paint that bubbles, skirting that swells. And at night, when the house goes quiet, the faint hiss of running water with every tap firmly off.
The boiler is a witness too: sealed-system pressure that keeps sliding down is water escaping somewhere. In the older terraces near the town centre and the mill-village streets at Sion Mills, where pipework has been patched in stages over a long lifetime, slow weeps at ageing joints deserve a look sooner rather than later — one tired joint tends to have neighbours.
Everything off, stopcock closed, then watch. If the damp stops growing or the hiss stops, it's your side of the boundary — and honestly, that's as much as a home test can prove.
Turn off every tap, the washing machine, the dishwasher — anything that draws water. Close the main stopcock. Now observe: does the hiss go silent? Does the damp patch stop spreading over the next few hours? If yes, the water was coming through your own pipework. If the water keeps coming with your stopcock shut — or it's surfacing outside in the garden or footpath — the trouble is likely on the supply pipe or the public main, and NI Water is the right call for a suspected mains leak.
If your home has a water meter — most in Northern Ireland don't — there's a sharper version: read the meter, use no water at all for 30 to 60 minutes, and read it again. Movement on a still house means water escaping somewhere. Note down what you find; it's exactly what the plumber will ask when you ring.
Because the heating system is its own sealed loop of pipework — and it can leak into places you'll never casually see. Repeated top-ups are the symptom, not the cure.
A sealed heating system should hold its pressure. When the gauge keeps sagging below 1 bar days after a top-up, the water is going somewhere: a weeping radiator valve, a joint under the floorboards, a pinhole in a pipe buried in screed. Because heating pipework runs under floors and through voids, a small heating leak can go months without showing — sometimes the first visible sign is a stain on a downstairs ceiling, or nothing at all but the falling needle.
Top up once and watch the pattern. If it holds, fine. If it falls again within days, stop feeding it and have the system traced properly — every top-up is just feeding the leak. Our boiler problems guide covers the pressure story in full.
The moment water goes near electrics, a ceiling sags or bulges, or a patch is visibly spreading. Those three mean stopcock off and phone in hand — tonight, not next week.
Most hidden leaks are slow, and slow buys you time to test, observe and book a sensible daytime visit. Three situations take that time away. Water anywhere near sockets, light fittings or the consumer unit — turn the electricity off at the consumer unit if you can reach it without standing in water. A ceiling that's sagging or bulging — stay clear of it; if there's just a small bulge, piercing it gently with something thin over a bucket lets the water down in a controlled way. And a damp patch that's growing while you watch — that's not a weep any more, that's a flow.
In all three cases: stopcock closed, then ring. Tell the plumber what you saw and how fast things were moving. A leak you've already narrowed down is a shorter visit than a mystery.
Only if your home has a water meter — and most homes in Northern Ireland don't, so an unexplained jump in a bill isn't the warning sign here that it is elsewhere. That makes the physical clues matter more: damp patches, stains, the hiss of running water when everything is off, and a boiler gauge that keeps sliding down.
Yes — a slow weep at a joint under a floor or inside a wall can lose water for months in complete silence. That's why the signs are usually secondary: a musty smell in one room, skirting or flooring that swells, paint that bubbles, a stain that creeps. If the house goes quiet at night, listen near where the pipes run; a faint hiss is worth taking seriously.
Not necessarily. It might be the scar of an old, fixed problem — or a slow, intermittent leak that only runs when a particular fixture is used. Mark the edge of the stain in pencil with the date, then check it after baths, showers and heavy rain. If it grows, you've caught your culprit's habits, and that detail genuinely helps whoever comes to trace it.
Usually not. A plumber narrows things down before anything is opened up — isolating sections of pipework, checking the obvious joints and fittings first, and using the pattern of the damp itself as a map. Honest answer: sometimes a floorboard or a patch of plasterboard does have to come up, but a traced leak means one careful opening rather than exploratory demolition.
The main page — how the line works and the areas it covers.
Go to home →The first five minutes, in the right order.
Read the bulletin →Falling pressure, no heat, fault codes — and gas safety.
Read the bulletin →What to try yourself and when it's NI Water's sewer, not yours.
Read the bulletin →Honest ballparks and the questions to ask before work starts.
Read the bulletin →Pressure, controls, the immersion — the checks before you call.
Read the bulletin →Thawing safely with gentle heat — and the lagging that prevents it.
Read the bulletin →Ring any hour to be put through to a local plumber covering Strabane and the surrounding towns and townlands — stopcock test results at the ready.
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