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Cold taps and a family queueing for the shower. Before you ring anyone, there are four or five checks that fix a surprising share of these calls — and one rule that overrides the lot.
The short version: check the boiler has power, the thermostat and timer are actually asking for hot water, the pressure gauge sits around 1 to 1.5 bar cold, and — on a frosty morning — whether the condensate pipe outside has frozen. If you smell gas, none of that matters: get out and call 0800 111 999 first. Otherwise ring 020 4577 2888 to be put through to a local plumber, any hour.
A good share of "no hot water" turns out to be a switch, a setting or a pressure gauge — five minutes of looking, no tools, nothing opened up.
If the display is dead and it's not the switch or fuse, or the checks above change nothing, that's the end of the safe DIY list. Hand it over.
On a combi boiler, radiators hot while the hot tap runs cold is the textbook sign of a diverter valve playing up — the part inside the boiler that switches between heating the house and heating the tap water. When it sticks, you get one or the other, not both. There's no dial to turn and no reset that fixes it; the part lives behind the casing, which puts it firmly out of DIY reach. What you can do is say those exact words on the phone — "heating works, hot tap doesn't" — because that one sentence points straight at the fault. And for anything on the gas side of a boiler, the person doing the work must be on the Gas Safe register. Ask to see the card; a genuine engineer expects it.
Plenty of homes around Dungannon — especially older and rural ones — heat water in a cylinder rather than on demand. If yours has an immersion heater, you have a backup the combi household doesn't: flick its switch and the element heats a tankful off the electricity while the boiler side waits for a proper look. Check the immersion's own switch and its fuse or breaker at the consumer unit if nothing seems to happen. It's dearer per tank than gas or oil, so it's a stopgap, not a lifestyle. One more cylinder-country quirk: a hot tap that spits and sputters usually has an airlock — trapped air, often after the system's been drained — rather than a dead boiler. Sometimes it clears itself with gentle running; if not, it needs bleeding out, and that's a quick job for a plumber.
Whatever the fix turns out to be, ask for a price — or a call-out fee plus hourly rate — before any work starts. Same rule as every job on this site.
Because that's when the condensate pipe freezes. It's the small plastic pipe carrying the boiler's waste water to a drain, often along an outside wall, and when it blocks with ice the boiler locks out to protect itself — no heat, no hot water, first hard frost of the winter. Around Dungannon the exposed gable ends and outbuilding walls of rural properties get it worst. Thaw the pipe with warm water or a hot water bottle, reset once, and get it lagged so the next frost doesn't repeat the trick — the boiler problems guide covers it step by step. If cold weather has stopped a tap dead rather than the boiler, that's a different beast: see the frozen pipes guide before anything splits.
On a combi boiler that's the classic sign of a sticking diverter valve — the part that switches the boiler between heating the radiators and heating the tap water. It's not something to poke at yourself: the fix sits inside the boiler, so it's a job for a professional. Say exactly that symptom when you call and you've saved half the diagnosis.
Once, yes — most sealed systems want about 1 to 1.5 bar when cold, and the manual shows how to top up through the filling loop. Close the loop properly afterwards. If the pressure keeps falling over days or weeks, the water is escaping somewhere, and that leak needs finding rather than another top-up.
Yes — that's what it's for. If your cylinder has an immersion heater, its own switch (often labelled, sometimes with a red neon) will heat a tank of water off the electricity while the boiler side gets sorted. Check the switch hasn't tripped at the consumer unit. It costs more per tank than gas or oil, so treat it as the spare wheel, not the engine.
Usually an airlock — a pocket of air trapped in the pipework, often after the system has been drained or worked on. Sometimes running the tap gently for a while shifts it; sometimes it needs bleeding out properly. If a tap goes from sputtering to nothing in freezing weather, think frozen pipe instead and go read the frozen pipes guide.
Forget the hot water. Get everyone out of the property — no light switches, no flames, no hunting for the leak. From outside, at a safe distance, call the National Gas Emergency Service on 0800 111 999 and follow their instructions. Only go back in when you're told it's safe.
The main page — how the line works and who it covers.
Go to home →Pressure, error codes, frozen condensate — and the gas rule.
Read the guide →Stopcock off first — the right order for the first five minutes.
Read the guide →Gentle heat from the tap end back — and never a flame.
Read the guide →Damp patches, dropping pressure and the honest stopcock test.
Read the guide →What to try, what to never pour, when it's NI Water's job.
Read the guide →How the bill is built and what to pin down first.
Read the guide →Any hour, any day — you'll be put through to a local plumber covering Dungannon and the surrounding towns and villages.
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