Boiler emergency guide

Boiler Breakdown Emergency Guide: What to Do When Your Heating Fails

If your boiler has stopped working, start with safety. This guide explains what to check yourself, when to stop, and when to call a Gas Safe registered engineer.

Need repair help in Harrow?

For a boiler fault that will not reset, book a local repair visit.

Boiler repair Harrow Call 075700 54100

First: rule out gas and carbon monoxide danger

If you smell gas

  • Turn off the gas at the meter if it is safe to do so.
  • Open doors and windows.
  • Do not smoke, use naked flames, or operate electrical switches.
  • Leave the property if the smell is strong.
  • Call the National Gas Emergency Service on 0800 111 999.

If carbon monoxide is possible

Warning signs can include headaches, dizziness, nausea, tiredness, confusion, chest pain or flu-like symptoms that improve away from the property.

Get fresh air immediately and call 999 if anyone is unwell.

Quick answer: what should I do if my boiler breaks down?

  1. Check for gas smell, carbon monoxide symptoms, leaks or scorch marks. If present, stop and call emergency help.
  2. Check the thermostat, timer and power supply.
  3. Look at the boiler pressure gauge. Many boilers need around 1.0 to 2.0 bar when cold.
  4. Write down any error code shown on the boiler display.
  5. Try one reset only if the manual says it is safe.
  6. Call a Gas Safe engineer if the fault returns, the boiler leaks, pressure keeps dropping, or there is still no heating or hot water.

Safe checks you can do before calling an engineer

Check the heating is switched on, the room thermostat is set above room temperature, and the timer or programmer is not set to off. Replace thermostat batteries if the display is blank.

Confirm the boiler display is on and check whether a fuse spur, switch or circuit breaker has tripped. If the boiler repeatedly loses power, stop resetting it and book an engineer.

Low pressure is a common cause of no heating. If the gauge is below 1 bar, check for leaks before repressurising. Only use the filling loop if you know how and your boiler manual allows it.

Note the error code before pressing reset. Try one reset only if it is safe. Repeated lockouts usually mean there is an underlying fault.

If the boiler shows a condensate or ignition fault during freezing weather, the outside condensate pipe may be frozen. Warm water, not boiling water, can be poured over the pipe end if it is safe to reach.

Common boiler breakdown symptoms

No heating or hot water

Check thermostat, timer, pressure and error code. If the boiler will not fire or keeps locking out, book a repair.

Boiler pressure is low

Low pressure may be caused by leaks, recently bled radiators, a faulty expansion vessel or pressure relief valve.

Boiler is making loud noises

Banging, kettling or gurgling can point to air, sludge, pump problems or restricted flow.

Boiler keeps switching off

Repeated shutdowns can be caused by pressure faults, overheating, blocked condensate, pump issues or ignition faults.

Water leaking from boiler

Turn the boiler off and call an engineer. Do not remove the boiler casing or try to repair internal parts.

Error code on display

Write down the code and boiler brand. This helps the engineer diagnose the likely fault faster.

Useful emergency numbers

Related local help

Boiler breakdown FAQs

Check for gas smell, carbon monoxide symptoms, leaks, scorch marks or unsafe flame colour. If any are present, stop using the boiler and call emergency help or a Gas Safe engineer.

You can try one reset if the boiler manual says it is safe and there are no danger signs. If the fault returns, do not keep resetting it.

Repeated pressure loss can be caused by a leak, faulty pressure relief valve, expansion vessel issue or recent radiator bleeding. It should be checked by an engineer.

It is an emergency if there is gas smell, carbon monoxide concern, leaking water near electrics, scorch marks, unsafe flame colour or no heating for a vulnerable household.

Gas boiler repairs should be carried out by a Gas Safe registered engineer. Do not remove the boiler casing or work on gas components yourself.

Still no heating or hot water?

Book a local Harrow boiler repair visit with Harrow Heating.

Boiler repair Harrow Call 075700 54100
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