Boiler will not ignite
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →⚠️ If you smell gas at any point, do NOT attempt to reset the boiler. Evacuate the property and call the National Gas Emergency Service on 0800 111 999 immediately.
A boiler that won't ignite is one of the most common heating problems UK homeowners face, particularly as boilers age or during the colder months when demand is highest. When your boiler attempts to fire but fails repeatedly, it usually locks out as a safety measure and displays a fault code on the control panel. This can leave you without heating and hot water at the worst possible time. The good news is that many ignition faults can be traced to simple issues like low pressure, depleted gas credit, or a tripped reset switch—problems you can often check yourself before calling an engineer. However, some ignition faults require professional diagnosis and repair, as they may involve internal components like the spark electrode or gas valve that only a Gas Safe registered engineer is legally permitted to service.
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Most likely cause & what to check
Before calling an engineer, check the basics: is the gas supply on? Check another gas appliance (gas cooker or fire) to confirm gas is reaching the property.
Check your prepayment gas meter if applicable — ensure it has credit. Emergency credit may be available outside business hours.
Check the boiler pressure — a reading below 0.5 bar or above 3 bar will prevent ignition on most modern boilers. Repressurise to 1–1.5 bar using the filling loop if pressure is low.
Press the reset button (hold 3–5 seconds). If the boiler attempts to ignite and then locks out again, do not keep resetting — repeated lockouts can indicate a dangerous fault.
Note down the fault code on the display and call a Gas Safe registered engineer. Common ignition faults include a failed ignitor, spark electrode, or gas valve.
Do not attempt to open the boiler casing or adjust the gas valve yourself — this is illegal under the Gas Safety (Installation and Use) Regulations 1998.
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Frequently asked questions
Why is my boiler not igniting but gas is still connected?
Gas reaching your property doesn't guarantee it's reaching the boiler safely. Low water pressure (below 0.5 bar), a faulty spark electrode, a stuck gas valve, or an ignition control fault can all prevent ignition even with gas supply present. Check your boiler pressure gauge first, then note any fault code before contacting an engineer.
Is it safe to keep pressing the reset button on my boiler?
No—pressing the reset button repeatedly can mask a potentially dangerous fault and may damage the boiler's safety lockout system. If your boiler ignites once then locks out again immediately, stop resetting and contact a Gas Safe engineer instead.
How do I know if my boiler pressure is too low?
Most modern boilers have a pressure gauge on the front showing a needle or digital reading. A reading below 0.5 bar will prevent ignition; aim for 1–1.5 bar. If it's low, use the filling loop (usually two handles beneath the boiler) to repressurise by slowly opening both taps until pressure reaches the safe range.
What does a boiler ignition fault code mean and can I fix it myself?
Fault codes are diagnostic messages indicating what the boiler's safety system has detected—common ignition codes point to a failed spark electrode, ignitor, or faulty gas valve. You cannot safely repair these yourself; write down the code and call a Gas Safe registered engineer, as opening the boiler or adjusting the gas valve is illegal without certification.
Can a prepayment gas meter cause ignition problems?
Yes—if your prepayment meter runs out of credit, gas will be cut off and your boiler won't ignite. Check your meter balance immediately, as emergency credit may be available outside business hours through your gas supplier.
Should I worry if I smell gas when my boiler won't ignite?
Yes—gas smell combined with ignition failure can indicate a leak or unsafe combustion issue. Do not reset the boiler; evacuate your home immediately and ring the National Gas Emergency Service on 0800 111 999.