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Defrosting a frozen boiler condensate pipe

Posted on: Thu 17th January, 2019

Gurgling or bubbling sounds coming from your boiler? When the weather turns colder, your boiler condensate pipe may freeze. Here are a few tips that may help you get your boiler working again.

What is a condensate pipe?

A condensate pipe carries condensation from your boiler to your outside drain. It's usually a white, grey or black plastic pipe that travels from your boiler through the external wall directly outside where your boiler is located.

During cold weather the condensation in the pipe may freeze and cause a blockage making the condensate back up into the boiler and cause a shutdown.

How to defrost the pipe

If you think the boiler condensate pipe has frozen, the following steps should help get things back to normal quickly.

  1. Confirm the condensate pipe is frozen
    There may be a fault code or a warning light on your boiler’s display. Gurgling or bubbling sounds coming from the boiler or the condensate pipe are another sign that the condensate pipe has frozen.
  2. Locate the blockage
    The pipe is probably frozen at its most exposed point. This may be the open end of the pipe, or at a bend or elbow. Running your hands over the pipe until you find a section that feels colder than the rest should help you identify the blockage quickly.
  3. Thaw the pipe
    Using a jug or watering can, pour warm water along the length of the pipe, repeating the process until the pipe has thawed. Don’t use boiling water as this can crack or damage the pipe. Alternatively, you can use a hot water bottle or a heat pack to slowly defrost the pipe.
  4. Restart your boiler
    Once the frozen section has been melted and cleared, check your boiler manual for instructions on how to reset the boiler correctly. Your boiler should now restart correctly.

If this process doesn’t work, you can call us on 0300 303 1190 

Here is a handy example video of how to defrost your condensate pipe. Please note: you may get different error codes on your boiler, as this video is for a Worcester Bosch boiler.