Condensate pipe frozen: boiler not working (UK winter fix)

What to check (in order)

1. Check the weather: has it been below 0°C overnight?
2. Check the boiler display for a fault code (often related to condensate/drainage). Note it down.
3. Locate the condensate pipe (usually a white/grey plastic pipe from boiler to outside drain).
4. Find the likely freeze point: external run, near a bend, or where it enters a gully.
5. Thaw gently: pour warm (not boiling) water over the frozen section, or wrap a warm cloth around it.
6. Once thawed, reset the boiler once and observe.

What the result means

• Boiler restarts: frozen condensate was likely the cause (monitor).
• Keeps failing in cold snaps: external run may be poorly insulated/too long/incorrect fall — needs improvement.
• No change: fault may be elsewhere; use code/manual for next steps.

What you can safely do

• Use warm water only to thaw the frozen section.
• Target the outside plastic condensate pipe rather than the boiler itself.
• Reset the boiler once after thawing and observe.
• Stop if the area is unsafe or you cannot access the pipe safely.

Engineer notes

Check condensate route: fall (gradient), diameter, trap integrity, external length, termination type. For repeat cases, improve insulation and routing; consider internal termination or approved trace heating where appropriate. Confirm syphon/trap not blocked and that condensate discharge meets manufacturer guidance.