Frozen condensate pipe: how to get your boiler working again

In a cold snap, one of the most common reasons a boiler stops working is a frozen condensate pipe. The good news is that it is often simple to fix.

What is a condensate pipe?

Modern condensing boilers produce acidic water as they work. A plastic pipe, usually grey or white, carries this water away to a drain. If part of the pipe runs outside, the water inside can freeze and block it, and the boiler shuts down to protect itself.

Signs of a frozen condensate pipe

• The boiler stops working during freezing weather.

• A fault code appears on the display, which your manual will explain.

• You hear gurgling from the boiler or pipe.

How to thaw it safely

1. Find where the pipe leaves the house and look for the frozen section, often at a bend or the open end.

2. Pour warm water, not boiling water, slowly over the pipe. Boiling water can crack plastic pipes.

3. Alternatively, hold a warm water bottle or heat pack against the pipe.

4. When the pipe is clear, reset the boiler following the manual.

Only work at ground level. If the pipe is high up, do not climb a ladder in icy weather; call an engineer instead.

Stopping it happening again

• Insulate external condensate pipework with weatherproof lagging.

• Increase the pipe diameter on long external runs.

• Re-route the pipe internally to a waste pipe where possible.

Need an engineer?

The Essential Connection repairs boilers across Walton-on-Thames, Weybridge, Cobham, Esher, Kingston and South West London. Get in touch or call 07719 664615.