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A cold tap breeds two bad instincts: assuming the boiler is dead, and going hunting inside it. Neither survives contact with the facts. Here's the short list of checks that are genuinely yours to make — and the line you never cross.
No hot water right now? Check the boiler's pressure gauge (around 1 to 1.5 bar cold is typical), make sure the thermostat and timer are actually asking for hot water, and look for a tripped switch or fuse at the consumer unit. Still cold? Call 020 4577 2888 to be connected with a local plumber, any hour. If you smell gas, skip everything: leave the property and call 0800 111 999.
Before declaring the boiler dead, spend two honest minutes on the things that merely pretend to be boiler faults: a thermostat turned down below room temperature, a timer or schedule that quietly reverted after a power cut, a hot-water setting knocked off on the boiler itself, or a tripped switch at the consumer unit. It feels too simple to be the answer, which is exactly why it so often is.
MythIf the water's gone cold, something expensive has failed.
FactThe cheapest faults are the commonest ones. Low pressure alone will stop many boilers heating anything: most sealed systems want roughly 1 to 1.5 bar when cold, and topping up through the filling loop — following your model's manual — often brings hot water straight back. The caveat this site repeats deliberately: topping up every week isn't maintenance, it's a leak being ignored on a schedule.
MythHot radiators prove the boiler is fine — the taps must be the problem.
FactOn a combi boiler, warm radiators with cold taps (or the reverse) is a recognised fault pattern of its own — very often a diverter valve sticking, the part that switches the boiler's output between heating and hot water. The taps are innocent. It's a job for a professional, but noticing which half works turns a vague "boiler's acting up" into a genuinely useful description when you call.
Homes with a hot water cylinder — common in Portadown's older terraces where the airing cupboard still earns its name — usually have an immersion heater: an electric backup element with its own switch, often labelled and often forgotten. If the boiler is sulking, the immersion can heat a tank of water while you sort the real fault in daylight hours instead of at emergency rates. And if only one hot tap has failed rather than all of them, suspect an airlock in the pipework rather than the boiler at all.
In a frosty snap, a boiler that stopped overnight has a prime suspect: the condensate pipe, especially where it runs down an outside wall — a classic on the newer estates around Portadown and Craigavon. Many boilers shut down in protest when it freezes, and pouring warm (not boiling) water along the pipe, then resetting, often revives everything without a visit.
MythHandy with a screwdriver? The boiler casing is fair game.
FactEverything behind the casing of a gas boiler is legally reserved for an engineer on the Gas Safe Register — that's the law, not gatekeeping. Your territory is the outside: gauge, controls, filling loop, reset button, the switch on the wall. The moment a fix would involve removing the case, the job has changed hands.
On a combi boiler that split is the classic signature of a sticking diverter valve — the component that switches the boiler's effort between radiators and taps. It isn't something to poke at yourself; note which side works, tell the person you call, and you've already done half the diagnosis.
No — and this one has no exceptions. Anything behind the casing of a gas boiler is legally work for an engineer on the Gas Safe Register. The checks that are yours to make all live outside the case: the pressure gauge, the thermostat, the timer, the reset button and the switch on the wall.
Most sealed systems sit around 1 to 1.5 bar when cold, and many boilers refuse to heat water below roughly 1 bar. Topping up via the filling loop — following your model's manual — usually restores it. If the pressure keeps sliding down over days or weeks, that's a leak wanting to be found, not a gauge wanting another top-up.
If just one hot tap has died — especially after pipework has been drained or a cylinder refilled — trapped air is a fair suspect. Airlocks sometimes clear themselves, and a plumber can clear a stubborn one quickly. Every hot tap failing at once points at the boiler or cylinder instead, which is a different phone call.
Stop checking anything. Leave the property without touching switches, appliances or naked flames, and once you're at a safe distance call the National Gas Emergency Service on 0800 111 999. Hot water can wait; that call can't. Only go back inside when you're told it is safe.
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 →Gentle heat from the tap end, never a flame — and the lagging that prevents it all.
Read the guide →Damp patches, dropping pressure and the honest stopcock test.
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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