Home › No Hot Water
Four short stops before you write the boiler off — pressure, controls, the trip switch, and the immersion heater in reserve.
No hot water — what do I check first? Look at the boiler's pressure gauge, check the thermostat and timer haven't been knocked, and see whether a switch has tripped at the consumer unit. If none of that explains it, and there's an immersion heater, that can carry you through in the meantime. Still nothing? Ring 020 4577 2888 to be put through to a local plumber.
Check pressure first — below about 1 bar, many boilers won't fire hot water properly. Listen for it attempting to light, and glance for any error light or code.
Stand at the boiler for a moment. Is the display lit at all? Does it click and attempt to fire when you run a hot tap, or stay silent? A gauge sitting below roughly 1 bar is the single most common reason a boiler quietly stops delivering hot water while still technically "on" — a one-off top-up through the filling loop, following your manual, often has water running hot again within minutes.
If you're on oil, as plenty of households across rural Lecale are, check there's actually fuel in the tank and that the burner isn't showing a lockout light — an empty tank presents almost identically to a "dead" boiler otherwise. Either fuel, if the boiler shows a fault code or a lockout that won't clear on one reset, that's your answer: something needs a professional look, not another reset.
Thermostats get nudged, timers get knocked out by power cuts, and both look exactly like a broken boiler. Worth two minutes before assuming the worst.
A cylinder thermostat turned down by a well-meaning visitor, a hot water programmer that lost its schedule after a power cut, or a "summer/winter" switch left in the wrong position can all present as no hot water with an otherwise perfectly healthy boiler. Check the programmer is actually calling for hot water at this time of day, and that any room or cylinder thermostat is set somewhere sensible rather than down at its lowest notch.
If your system has a separate hot water cylinder — common in the older housing stock around the town centre — also check whether the heating works while the hot water doesn't, or vice versa. That split is a genuinely useful clue, and worth passing on to the plumber rather than working out alone.
A tripped switch cuts power to the boiler or the immersion heater without any other warning. One flick back on is a fair test; a repeat trip means stop and call.
Open the consumer unit and look for a switch sitting in a different position to its neighbours — that's usually enough to spot it without needing to know exactly what each one does. Reset it once. If power holds and the boiler springs back to life, you've found and fixed the fault yourself, no charge, no drama.
If it trips again the moment you reset it, though, stop there. That's a genuine electrical fault somewhere in the circuit — a failing element, damp got into a connection, a fault in the boiler's own electronics — and repeated resetting risks a shock or, in the worst case, a fire. Leave it off and make the call; describe exactly what tripped and how quickly.
If you have a hot water cylinder, the immersion heater is a genuine backup — a separate electric element that doesn't need the boiler at all. Not every system has one, but plenty do.
Homes with a hot water cylinder in an airing cupboard usually have an immersion heater built in as standard, wired to its own switch, often labelled right there on the airing cupboard wall or at the consumer unit. Flip it on and give it 30 to 60 minutes and you'll usually have a tank of hot water for washing up and showers while the boiler fault gets sorted properly — genuinely useful on a cold evening with children in the house.
It costs more to run than the boiler day to day, so it's a stopgap rather than a long-term plan, and if it won't switch on or trips the consumer unit itself, that's worth mentioning alongside the main fault when you call — it may be a second, unrelated problem, or it may be the same one showing itself twice.
A common cause is a cylinder thermostat set too low or failing, or on an unvented cylinder, a heating element on its way out. It can also mean the boiler is firing but underperforming — a partial blockage or a heat exchanger that needs a service. Worth mentioning to the plumber which taps run lukewarm, and for how long.
On a combi boiler, that split points at a diverter valve stuck on the heating side, or a faulty flow sensor that isn't recognising a tap has opened. On a system with a hot water cylinder, it more often points at the cylinder thermostat or its motorised valve. Either way, it's useful information to give the plumber before they arrive.
Flicking it back on once is reasonable. If it trips again immediately, stop — that's an electrical fault, not a fluke, and repeated resetting risks a shock or a fire. Leave it off and get it looked at, particularly on an older immersion heater that's never been serviced.
If your heating and taps are fed straight from a combi boiler, there's no separate cylinder to blame — the fault sits with the boiler or its controls. If you have a hot water cylinder in an airing cupboard, the boiler can be working perfectly while the cylinder's thermostat, coil or immersion element has failed. Knowing which system you have narrows the search a lot.
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 guide →Pressure drops, error codes — and gas safety.
Read the guide →What to try yourself and when it's the sewer, not your drain.
Read the guide →Honest ballparks and the questions to ask before work starts.
Read the guide →Thawing safely with gentle heat — and the lagging that prevents it.
Read the guide →Damp patches, dropping pressure and the stopcock test.
Read the guide →Ring any hour to be put through to a local plumber covering Downpatrick and the Lecale country around it.
Call now