What to do if your boiler breaks down
Save £100–300 in 30 mins — no heating engineer needed
Most people call a heating engineer for this. You probably don't need to.
Last updated: March 2025
Only basic tools needed — most homes already have them.
Before you start
Most boiler faults have simple causes — low pressure, a tripped circuit, or an error code with a known fix. Work through this checklist before paying for an engineer call-out.
If you smell gas at any point: do not touch any switches, leave the house immediately, and call the National Gas Emergency line on 0800 111 999.
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Tools & materials
- ✓Boiler manual— often kept in a kitchen drawer or downloadable from the manufacturer's website using the model number
- ✓Nothing else needed— all the checks are visual
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Check the pressure gauge
Look at the pressure gauge on the boiler front. It should read 1–1.5 bar. Below 1 bar means the system needs repressurising — see our repressurising guide. This is the most common cause of a boiler stopping.
Most people get this done in under 5 minutes.
Where beginners go wrong
Repeatedly pressing reset without fixing the underlying fault — the boiler will just lock out again and could make the fault worse.
Pouring boiling water on a frozen condensate pipe — use warm water; boiling can crack the plastic pipe.
Ignoring a gas smell to try the checklist — gas smell means leave the building and call the emergency line immediately.
Stop and call a Gas Safe heating engineer if...
You smell gas — leave immediately and call 0800 111 999
The boiler resets but locks out again within minutes
There is water leaking from inside the boiler casing
Cost breakdown
Recommended starter kit
Five tools that cover most home repairs.
- →Adjustable spannerAmazon·Screwfix
- →Screwdriver setAmazon·Screwfix
- →PTFE tapeAmazon·Screwfix
- →Spirit levelAmazon·Screwfix
- →Tape measureAmazon·Screwfix
Want everything in one go? Get it on Amazon
What you just learned
You now know how to diagnose the most common boiler faults, read error codes, and understand when a problem is fixable yourself and when you need a professional.
What this unlocks
With this knowledge, you can handle repressurise fixes, frozen condensate faults, and tripped circuits yourself — and have a much more informed conversation with an engineer when you do need one.
Most people would pay a tradesperson for this.
⚠️ Watch out if you rent
A broken boiler in winter is an emergency. Landlords must fix heating and hot water within 24 hours in cold weather. Contact them immediately in writing, keep a record, and if they do not act, contact your local council Environmental Health team.