Five minutes of honest checks — gauge, controls, switches — before anyone pays for a call-out. For homes in Coleraine and along the north coast.
Most "no hot water" calls come down to four things: boiler pressure that's dropped below the roughly 1 to 1.5 bar most combis want when cold, a thermostat or timer that's been knocked, a tripped switch or fuse, or — on a combi — a stuck diverter valve, where the heating works but the taps run cold. Check those in that order. If you smell gas, skip everything: leave the property and call 0800 111 999 from outside.
Leave the property now. Don't touch light switches, sockets or anything electrical on the way out, don't use naked flames, and don't stop to hunt for the leak.
Once you're safely outside, call the National Gas Emergency Number on 0800 111 999. A plumbing line is not the right contact for a suspected gas leak — call a plumber only after the gas emergency service has made things safe.
Start at the gauge on the front of the boiler. Around 1 to 1.5 bar with the system cold is typical for most combis — the manual gives the exact range for your model. If the needle has sunk well below that, many boilers simply lock out and refuse to heat water at all. A top-up through the filling loop, following the manual's steps, often brings everything back within minutes. But if you're topping up every week, the system is losing water somewhere, and that's a fault worth tracing rather than a ritual worth keeping.
Some of the older properties around Coleraine still run aging boiler installations that were fine decades ago but are more prone to leaks, corrosion and pressure problems now — so a gauge that won't hold its number deserves a proper look.
That combination is worth noticing, because it narrows things down fast. On a combi boiler, a diverter valve switches the burner's effort between the radiators and the hot taps; when it sticks, one side works and the other doesn't. Check the obvious first — thermostat, timer and programmer haven't been knocked or reset, and hot water is actually scheduled on. If the controls are fine and the pattern persists, the valve is a diagnosis job for a professional, not something to dismantle yourself.
Plenty of homes around Coleraine and the surrounding villages heat water in a cylinder rather than on demand. The checklist changes slightly: make sure the cylinder thermostat hasn't been nudged down, the programmer is calling for hot water at the times you expect, and the immersion heater — the electric backup, usually fed from its own wall switch near the cylinder — hasn't tripped or been switched off. The immersion is also your stopgap: if the boiler side has failed, it can usually keep hot water coming while you arrange a repair. If the immersion runs but the water stays stubbornly cold, the element itself may have failed, and that's a job for a professional.
One more seasonal note: along the coast towards Portstewart, Portrush and Castlerock, properties left unheated for weeks over winter often reveal their faults only when someone next turns everything on. If that someone is you, work down this page calmly — gauge, controls, switches, condensate pipe — before assuming the worst.
On a combi boiler, radiators working while the taps run cold is the classic sign of a stuck diverter valve — the part that switches the boiler between heating and hot water. Check the thermostat, timer and programmer settings first; if they're fine, the valve is a diagnosis job for a professional, not something to dismantle yourself.
Yes. If the gauge has dropped well below the roughly 1 to 1.5 bar most combis want when cold, the boiler can lock out and refuse to heat anything. A top-up through the filling loop, following your manual, often brings it back — but pressure that keeps dropping means water is escaping somewhere, and that needs investigating.
Check the cylinder thermostat hasn't been knocked down, the timer or programmer is actually calling for hot water, and the immersion heater switch — usually a wall switch near the cylinder — hasn't tripped or been turned off. If the immersion runs but the water stays cold, the element may have failed, which is a job for a professional.
No. Anything behind the casing is for a Gas Safe registered engineer, in Northern Ireland as everywhere else in the UK. Stick to the controls on the outside — the pressure gauge, thermostat, timer and reset button — and leave the rest sealed.
Quite possibly. In a cold snap, the condensate pipe that runs from the boiler to a drain outside can freeze, and many boilers shut down in protest. Thaw the outside section gently with warm — never boiling — water and reset once. If the boiler still won't run, it's time to call.
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 →Stopping pipes freezing in the first place, and thawing one safely.
Read the guide →Damp patches, dropping pressure, and the stopcock test that narrows it down.
Read the guide →The main page: what to do right now and the areas covered.
Go to home →This site connects callers with a local plumbing professional covering Coleraine, Portstewart, Articlave and the surrounding area — day or night. No gas emergencies: for gas, call 0800 111 999.
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