Pilot Light Keeps Going Out? Causes & Fixes UK 2026
Modern boilers often use electronic ignition instead of a permanent pilot light, but some older UK boilers still have a pilot that can go out. If your pilot keeps extinguishing, it can indicate a safety issue, a gas supply problem, or a failing component. This guide explains common causes, how to relight safely (at a high level), and when to call a Gas Safe engineer.
Safety First
If you smell gas, do not attempt to relight the pilot. Ventilate the area and follow UK gas emergency guidance. Never remove the boiler case or bypass safety devices.
Common Cause 1: Thermocouple Issues (Older Boilers)
Many pilot-light boilers use a thermocouple to prove the flame is present. If it’s worn, dirty, or failing, it can shut off the gas supply and the pilot will go out. This is a common cause and typically needs an engineer to replace or service.
Common Cause 2: Poor Gas Supply or Low Pressure
Interrupted gas supply, a partially closed isolation valve, or supply issues can stop the pilot staying lit. If other gas appliances are also affected, it’s more likely a supply problem than a boiler-only fault.
Common Cause 3: Flue or Ventilation Problems
Boilers need safe flueing. Issues like poor draught, blocked flues, or ventilation problems can cause safety shutoffs. Treat these as urgent and use a qualified engineer.
How to Relight Safely (High-Level)
Follow your boiler’s manual. Typically you switch the control to pilot, hold the ignition control while lighting, then keep holding briefly so the thermocouple warms. If it won’t stay lit after a couple of attempts, stop and call an engineer.
Replacing an Older Boiler? Start With kW Output
Persistent pilot problems can be a sign it’s time to upgrade. Use our calculator to estimate the right kW range before comparing replacement boilers.
Use the Boiler Size CalculatorFrequently Asked Questions
Do modern boilers have pilot lights?
Most modern boilers use electronic ignition and don’t have a permanent pilot. Pilot issues usually apply to older models.
Why does my pilot light go out when the boiler turns on?
It can be thermocouple issues, airflow/flue problems, or gas supply instability. An engineer can test safely.
Is it safe to relight a pilot light myself?
Many homeowners relight using the manual instructions, but if there’s any gas smell, repeated failures, or you’re unsure, call a Gas Safe engineer.
Can a blocked flue cause pilot issues?
Yes. Flue safety issues can trigger shutoff. Treat flue concerns as urgent and get professional help.
When should I replace the boiler?
If it’s old, inefficient, and repeatedly failing or parts are costly, replacement can be a better long-term decision.