Frozen Condensate Pipe: How to Fix It

Modern condensing boilers produce condensate — acidic water produced during the condensing process — which exits through a plastic pipe, usually through an outside wall. In temperatures below freezing, this pipe can ice up, causing the boiler to display a fault and lock out.

How to identify a frozen condensate pipe

The condensate pipe is a white or grey plastic pipe (usually 22mm or 32mm diameter) that exits your property and terminates at a drain. If your boiler shows a fault code in freezing weather and everything else is fine, the condensate pipe is the first thing to check.

How to thaw it safely

1. Find where the pipe exits the building and traces to the drain
2. Fill a jug with warm (not boiling) water — boiling water can crack the plastic
3. Pour it slowly over the frozen section from top to bottom
4. Alternatively, wrap a hot water bottle around the frozen section
5. Once the pipe is clear, reset your boiler

Preventing it next winter

Ask your engineer to insulate the exposed section of condensate pipe with foam pipe lagging — available for under £5 at any DIY store. Better still, if your boiler is being replaced, ask us to route the condensate pipe internally to an internal drain where possible.

Still not working?

If the boiler won't start after thawing the pipe, there may be a secondary fault. Call us for a same-day diagnosis in Corby and surrounding areas.