Central heating needs prompt assessment when it stops warming the home, leaks, repeatedly shuts down or develops persistent pressure or control problems. Urgency depends on the hazard, the indoor temperature and who relies on the heating. A gas smell, carbon monoxide alarm or suspected poisoning requires emergency action; a single cool radiator without other warning signs usually calls for a planned repair assessment.
Which signs need emergency action?
The NHS advises urgent medical help for suspected carbon monoxide poisoning. Call 111 for possible symptoms; call 999 if suspected exposure involves breathing difficulty, sudden confusion, unconsciousness, weakness, or chest or muscle pain. Do not drive yourself to hospital.
For smoke, fire or immediate danger to life, call 999. Keep away from water near electrical equipment. HSE advises that a gas appliance suspected to be unsafe should remain off until checked by a suitably qualified Gas Safe registered engineer.
Which heating faults need prompt attention?
These observations help explain the urgency. They do not identify the faulty component or establish that a replacement boiler is required.
Swipe across to read the table.
If water is escaping, our checklist for before a plumber arrives covers safe isolation and access preparation. Do not touch wet switches or remove equipment covers to trace a leak.
When does no heating become urgent?
A heating failure on a mild afternoon is different from losing heat overnight in cold weather. Explain the indoor temperature, whether it is falling and whether anyone has reduced mobility, is older or has a health condition affected by cold.
The Met Office recommends heating the home to at least 18°C, particularly for people aged 65 or over, those with reduced mobility and those with heart or lung conditions. This is health guidance, not a universal legal threshold or a rule that you must wait until a room reaches that temperature before calling.
If you cannot keep vulnerable occupants warm, arrange a safe warmer place while seeking help. Do not use a barbecue or camping stove indoors. The NHS warns that these can cause carbon monoxide to build up.
For the possible causes of a complete failure, see no heating or hot water: common causes. Here, the priority is deciding how quickly help is needed.
What can you check safely?
Only make these checks if there is no gas smell, alarm, suspected unsafe appliance, active electrical hazard or other immediate danger:
- Check the programmer's time, heating schedule and operating mode.
- Compare the thermostat setting with the displayed room temperature.
- Look for a battery warning on a battery-powered room control.
- Read the boiler display and photograph any fault code.
- Note the pressure reading without adjusting unfamiliar valves.
- Establish whether hot water and other heating zones still work.
Follow the user manual for permitted actions. Do not repeatedly reset a fault, bridge wiring, force valves or open the boiler casing. If the controls appear to be the issue, our guide to heating that does not respond to the thermostat covers that narrower problem.
For a high pressure reading, see safe checks for high boiler pressure. A gauge reading alone does not tell you which component needs repair.
Is the problem local or across the system?
One cold radiator, an entire cold floor and a complete loss of heating are useful distinctions. Tell the engineer which rooms are affected and whether the change was sudden or gradual.
For an isolated radiator problem, use our guide to a radiator that will not heat up. If a whole floor is affected, our article on heating working downstairs but not upstairs explains that pattern.
Do not assume uneven heating automatically means sludge, a failed pump or the need for power flushing. Likewise, new noise does not prove one particular fault. For boiler-centred noises, see boiler banging or whistling.
What should you say when arranging help?
Give your postcode, system type if known, the main symptom, when it began and any safety concern. Mention error codes, visible leaks, recent work and whether the household has heating and hot water.
For complete loss of heating with an unclear cause, explain that when calling so the attendance can be arranged appropriately. For a known boiler-specific fault, describe the appliance and displayed code. These details help direct the assessment without requiring you to diagnose it.
If you rent or use communal heating, notify the landlord or building manager through the repair process. Ask about availability, the initial charge, what assessment includes and approval for further work. Do not wait for routine servicing to report an active fault.