Boilers · every brand

Frozen boiler condensate pipe

A condensing boiler drains water through a plastic pipe, often outside. In freezing weather it can freeze, the water backs up and the boiler shuts down, often with a gurgling sound and a fault code.

  • 2 codes
  • 2 brands
  • Often easy to fix

The code on each brand

Same fault, different code. Each one opens a page with the maker's own checks and a verdict.

Can't read yours?

Check these first, whatever the brand

  1. Find the pipe

    It's the plastic pipe, usually white or grey, that runs from the bottom of the boiler through the wall to a drain outside.

  2. Find the frozen part

    It's usually where the pipe is most exposed: a bend, the open end, or a long run outside.

  3. Thaw it with warm water

    Pour warm, not boiling, water along the pipe, or hold a hot water bottle against it. Boiling water can crack the pipe.

  4. Reset the boiler

    Once it's thawed, reset the boiler the way your manual describes.

  5. Stop it happening again

    Lagging the outside pipe helps. A permanent fix, like a wider pipe or a new route, is a job for an engineer.

A frozen pipe often shows up as an ignition code rather than a condensate code: see boiler won't light.

When it's time for an engineer

If you can't reach the pipe safely, or the boiler still won't restart after thawing, call a Gas Safe engineer.

Parts people end up buying

Only once the checks point to a part. Match it to your model number: it's on a label on the data badge, usually under the boiler or behind the front cover.

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Questions people ask

How do I know if my condensate pipe is frozen?

The boiler stops in freezing weather, may gurgle, and shows a fault code, often an ignition or condensate code.

Can I pour boiling water on it?

No. Use warm water. Boiling water can crack the plastic pipe.

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