Emergency
Boiler Breakdown? What to Do While You Wait
Reviewed by our Gas Safe registered engineers · Last updated 22 July 2026
A boiler that’s died in the cold is stressful, but a few safe checks fix a surprising number of ‘breakdowns’ — and where they don’t, they tell us what to bring. Here’s what to try, what to leave alone, and how to stay warm and safe until we arrive.
Quick answer: Check the obvious first — is there power to the boiler, is the gas on (does the hob light?), is the pressure gauge between 1 and 1.5 bar, and is the thermostat calling for heat? Reset the boiler once if it’s showing a fault. If you smell gas, don’t touch any switches — turn off the gas at the meter, open windows, and call the National Gas Emergency line on 0800 111 999. For everything else, call us.
Triage
What the symptom is telling you
Match what your boiler is doing to the most likely cause. The colour on the left shows what’s safe to try yourself and what needs an engineer.
| The symptom | Likely cause | What to do |
|---|---|---|
| No power, blank display | Tripped fuse or a switch turned off | Check the fused spur and consumer unit, then switch it back on |
| Low-pressure warning or fault | Pressure has dropped below 1 bar | Top the pressure up to 1–1.5 bar using the filling loop |
| Locked out with a fault code | Ignition or safety lockout | Reset once; if it locks out again, an engineer is needed |
| Smell of gas | Possible gas escape | Turn off the gas at the meter, ventilate, and call 0800 111 999 — do not touch switches |
| Radiators warm but no hot water (combi) | Diverter valve fault | An engineer will free or replace the diverter valve |
| Banging then shutdown | Overheat lockout, possible pump or flow fault | Turn the boiler off and call us |
First Steps
What to try before you call
Quick checks to try
- Check the boiler has power — look for a tripped switch on the fused spur or consumer unit
- Check the pressure gauge reads 1–1.5 bar; top it up with the filling loop if it’s low
- Make sure the thermostat is calling for heat and the programmer is set to ON
- Reset the boiler once if it’s showing a fault code
Stop and get help if…
- You smell gas — turn off the gas at the meter, ventilate, and call 0800 111 999
- There’s a smell of burning or scorching, or black marks on the boiler
- The boiler locks out again straight after a reset
- Anyone feels unwell with headaches or dizziness (possible carbon monoxide)
Engineer Insight
What we usually find
A good third of the ‘breakdowns’ we’re called to on a cold morning aren’t breakdowns at all — it’s low pressure after a cold snap, a tripped switch, or a thermostat with a flat battery, all of which you can often sort in two minutes with the checks above. The ones that genuinely need us are lockouts that return after a reset, anything with a smell of gas or burning, and no hot water from a combi. For those, the sooner you call, the sooner we’re out — we keep 24/7 emergency slots for exactly this.
Costs
What a call-out typically costs
Typical North London guide prices — you’ll always get an upfront quote before any work starts.
FAQs
Boiler breakdowns — your questions answered
What should I check before calling an engineer?
Power to the boiler, gas supply (does the hob light?), pressure between 1 and 1.5 bar, and the thermostat set to call for heat. Reset the boiler once if it shows a fault. These four checks fix a lot of ‘breakdowns’ — and if they don’t, they tell us what to bring.
Is a boiler breakdown an emergency?
If you have no heating or hot water in cold weather, or there are vulnerable people in the home, treat it as urgent — we keep 24/7 slots. A smell of gas or burning is always an emergency: turn the boiler off and follow the gas-safety steps first.
How do I stay warm safely until you arrive?
Use extra layers and blankets, close doors to keep the heat in one room, and use a plug-in electric heater if you have one — never a gas hob or a paraffin or bottled-gas heater indoors, as those risk carbon monoxide.
Should I keep resetting my boiler?
Reset it once. If it fires up and stays on, great. If it locks out again, stop — repeated resets on a boiler with a genuine fault can cause more damage and, with some faults, aren’t safe. Call us instead.
What if I smell gas?
Don’t touch any electrical switches. Turn off the gas at the meter, open windows and doors, get everyone outside, and call the National Gas Emergency line on 0800 111 999. Only call us for the repair once it’s been made safe.
Related
Related guides
Work through why the boiler won’t start at all.
Read guideBoiler ProblemsBoiler Not IgnitingWhen it powers up but won’t light.
Read guidePressureBoiler Losing PressureLow pressure is a common breakdown cause.
Read guideHot WaterNo Hot WaterNo hot water but the heating’s still working?
Read guideLeaksBoiler Leaking WaterIf a leak is behind the breakdown.
Read guideMaintenanceSigns Your Boiler Needs ServicingServicing prevents most winter breakdowns.
Read guideBrowse all Boiler Problem guides, or head back to the Help & Advice Centre.
Boiler down? We keep 24/7 slots.
Book a Gas Safe engineer now, or call — we cover North London around the clock for breakdowns that can’t wait for morning.
Gas Safe Registered 918817 | North London specialists | Upfront pricing