How to safely unfreeze a frozen condensate pipe

With the colder weather on it's way, it's important that you keep you and your home warm.

If the temperature drops below freezing over the coming months, your boilers condensate pipe can freeze over, causing it to shut off. This can be a quick fix without the need to call a professional, have a read of our guide below.

What is a condensate pipe?
A condensate pipe carries condensation from your boiler to your outside drain. It's usually a white or grey plastic pipe that travels from your boiler through the wall directly outside where your boiler is located. During cold weather the condensation in this pipe may freeze and cause a blockage. This is turn causes the condensation to back up into the boiler and shutdown.

Frozen condensate pipe diagram


How to defrost the pipe?
If you suspect that your boiler condensate pipe has frozen, the following steps should help you get things back to normal quickly. 

  1. Confirm the condensate pipe is frozen 
    Depending on the make and model of your boiler, a frozen condensate pipe may be indicated by a 'fault code' or warning light on the 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 (not boiling water as this could crack or damage the pipe) water along the length of the pipe, repeating the process until the pipe has thawed. 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.