Pilot light keeps going out? Here's what's causing it
If you still have a pilot light your boiler is at least 15 years old, and the most common cause is a failing thermocouple. Simple fix, but on a boiler this age it's worth planning ahead.
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The likely causes, in order
- Failing thermocouple — The safety device that detects the pilot flame. When it weakens it can't sense the flame reliably and shuts off gas. £40 part, quick swap.
- Blocked pilot jet — Dust or debris in the pilot injector reduces flame size until it goes out.
- Draught — Poor flue draw or draughts around the boiler blow out the pilot. Usually needs flue inspection.
What you can safely try first
- Note how long the pilot stays lit — seconds vs hours indicates different faults
- Do NOT keep re-lighting repeatedly — you're releasing unburnt gas each time
Request a help · urgent quote in your area
Real engineer reply — usually within the hour during working times. Fixed written quote, no commission-driven sales, 12-month workmanship guarantee.
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- Fixed written quotes
- Manufacturer warranties up to 12 yrs
Frequently asked questions
Is it worth repairing a boiler this old?▾
Depends on efficiency. A 20+ year old boiler with a pilot light runs at 65-75% efficiency vs 92%+ for a modern condensing boiler. Replacement often pays back in 5-8 years.
Can you fit a modern replacement?▾
Yes — we specialise in conversions from old open-flue boilers to modern condensing combis or system boilers.
Related pages you might want
Still stuck? Get a real engineer on it
Call us if the DIY steps don't clear it — same-day response where possible, fixed price before any tools come out.