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A cold shower on a dark morning feels like an emergency. Most of the time, it's a five-minute check away from an answer — read the notices in order.
No hot water — where do I start? Check the boiler pressure gauge first, then confirm the timer or programmer is actually asking for hot water, then check for a tripped switch or blown fuse, and if there's a hot water cylinder, check its own thermostat and immersion. If none of that restores it, or you smell gas at any point, stop checking and ring 020 4577 2888 to be put through to a local plumber.
Below roughly 1 bar cold, many boilers refuse to fire at all — heating and hot water both. Top up once through the filling loop, following the manual.
The round gauge on the boiler's front is the first place to look, because low pressure is the single most common reason a boiler stops producing hot water, heating, or both. Most sealed systems are happiest between roughly 1 and 1.5 bar when cold; below about 1 bar, the boiler commonly locks out as a safety measure rather than limp along.
Repressurising through the filling loop — usually a braided silver hose or lever arrangement beneath the boiler casing — is a job most households can do with the manual open beside them: open the valves slowly, watch the needle climb to the target, close firmly, don't overshoot. If it holds and the hot water returns, good; if it needed topping up at all, note the date, because a boiler that needs the loop again within days is quietly losing water somewhere and deserves the attention covered in the hidden leaks notice.
A programmer set wrong, a dead timer battery, or a thermostat turned down can leave a perfectly healthy boiler simply not switched on. Rule this out before assuming a fault.
It sounds almost too simple to be worth a notice of its own, but a surprising share of "no hot water" calls trace back to a programmer that's been knocked off schedule, a clock that lost time after a power cut, or a hot water setting quietly switched to "off" while someone was adjusting the heating. Check that the programmer shows the correct time and day, that hot water is scheduled on or set to constant, and that any separate hot water dial or thermostat hasn't been wound down.
On combi boilers, try pressing the hot water demand or running a tap and watching whether the boiler's display shows it firing — a flame symbol or rising flow temperature confirms the unit is trying. If the boiler stays entirely silent and dark even when a tap is opened, that points away from the programmer and toward power or the unit itself, which the next two notices cover.
Boilers, immersion heaters and pumps all run on ordinary household electricity — check the fuse spur and consumer unit before assuming a plumbing fault.
Most boilers are wired through a fused spur near the unit, often with its own small switch and neon light; a tripped switch or blown fuse there will stop a boiler dead with no error code at all, because it has no power to display one. Check that switch, and check the consumer unit for a tripped breaker, particularly if the no-hot-water started right after another appliance was switched on or a storm passed through.
If a breaker keeps tripping the moment it's reset, stop resetting it — that pattern usually means a genuine electrical fault in the boiler, the immersion heater or the wiring to it, and repeated resets risk worse damage or a shock hazard. Leave it off and describe the tripping pattern when you ring; it tells the plumber or electrician a great deal before they arrive.
Older Carrickfergus terraces and many bungalows still run a hot water cylinder rather than a combi boiler — and that cylinder usually has its own electric immersion heater as a stand-in.
If your hot water comes from a tank in an airing cupboard rather than instantly from the boiler, the fault may sit with the cylinder's own thermostat rather than the boiler at all — a common pattern where the heating works fine but the hot water alone has failed. Most cylinders carry an immersion heater switched from a wall control, usually near the airing cupboard, marked with an on light. Switching it on and waiting an hour or two can restore hot water while the underlying fault is investigated, and it's worth doing as a stopgap on a cold night.
Be aware that an immersion left on constantly, rather than as a temporary measure, runs up the electricity bill quickly, so treat it as a bridge to the plumber's visit rather than a permanent fix. And if the immersion itself trips the switch or the water never warms even after a couple of hours, say so plainly when you ring — it usually means the element or thermostat inside the cylinder has failed, which is a job for a professional, not a DIY repair.
If you smell gas at any point during these checks, stop immediately, leave the property, and call the National Gas Emergency Service on 0800 111 999 from outside. That instruction overrides everything else on this page.
Much of Carrickfergus town runs on mains gas, while households further out towards Ballycarry, Straid and the townlands above Woodburn more often heat with oil. The pressure, timer and electrical checks above apply the same way regardless of fuel, but the last mile differs: an oil boiler with no hot water is worth a glance at the tank level, since a tank run low pulls air into the fuel line and can stop the burner firing even for hot water alone, needing the line bled before it will restart.
Whichever fuel you have, only a Gas Safe registered engineer may lawfully work on a gas appliance, and oil systems have their own competence schemes — asking to see identification when an engineer arrives is normal practice, not an insult. If every check above has been run and the water is still cold, that's the point to stop investigating and ring, with the pattern of what you found ready to describe.
On a combi boiler, that usually points at the diverter valve, which switches the boiler's output between heating and hot water and can stick or wear. On a cylinder system, it more often points at a failed cylinder thermostat or a faulty immersion element standing in for a boiler that isn't actually asking for hot water. Either fault needs an engineer to open the casing, so note what happens (heating works but taps run cold, or neither works) and ring.
Not necessarily. A single cold tap while the rest of the house runs hot water normally often points at an airlock in that branch of pipework, or a stuck non-return valve, rather than the boiler or cylinder itself. Try running the tap fully open for a minute, and check whether a nearby tap run at the same time restores flow. If it stays stubbornly cold alone, it's worth mentioning specifically when you ring.
Both can fail suddenly, but the visible symptom differs. A combi boiler tends to lose heating and hot water together, or show an error code, because one unit handles both. An older vented cylinder system can lose only the hot water while the heating carries on fine, because a separate thermostat, immersion or cylinder fault is involved. Telling the plumber which pattern you have shortens the visit considerably.
Stop checking anything and leave the property immediately. Don't touch light switches or strike a flame, and once you're safely outside, call the National Gas Emergency Service on 0800 111 999. This takes priority over every other notice on this page, and it isn't a job for a plumber to attend first.
The main notice — how the line works and the waters it covers.
Go to home →Close the stopcock before all else — the full standing orders.
Read the notice →Pressure, error codes, oil and gas — and the gas standing order.
Read the notice →What to attempt, and when it's NI Water's sewer instead.
Read the notice →How charging works and the questions to put before work starts.
Read the notice →Gentle thawing from the tap end, and never with a flame.
Read the notice →Damp patches, slipping pressure and the stopcock test.
Read the notice →Gauge checked, timer confirmed, switches tested? Then ring any hour and describe the pattern to a local plumber covering Carrickfergus and the villages around it.
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