How to fix a frozen condensate pipe

Author: Gregg
25th November 2022
4 min read

If you find that your boiler has stopped working after the cold weather has set in, there’s a chance it may be the result of a frozen condensate pipe. There is no need to panic however, as in this article we look at what and where a condensate pipe is, how you can tell if it’s frozen and how to fix it!


What is a condensate pipe?

As of 1st April 2005, all new gas boilers fitted in the UK must be condensing boilers- this means they convert water vapour condensation into heat making them more efficient. During the condensing process wastewater forms naturally, which needs to be removed. This water is transferred from the boiler to an external drain via the condensate pipe. Ideally, the condensate pipe will be connected to your waste internally, for example your kitchen sink, however this isn’t always possible and sometimes it runs externally.

If your condensate pipe runs externally, or the boiler is located somewhere that isn’t heated such as a garage, it’s very likely the condensate will freeze during the winter months which can cause your boiler to stop working.

How to find your boiler condensate pipe

The condensate pipe is made of plastic, usually white and connects to your boiler. If it’s connected to an external drain, you will find the condensate pipe exits the property through the closest external wall to the boiler and then runs down at an angle into your drainage system.

How do you tell if the condensate is frozen?

If you find that you’re without heating and hot water during winter, a frozen condensate may be the cause. If this is the case, you may hear the boiler making gurgling noises or you may find that the boiler is displaying a fault code which indicates the condensate is blocked. In both cases, it’s likely that the boiler will shut down- don’t worry though, the boiler does this to protect itself.


How to fix a frozen condensate pipe

The good news with a frozen condensate is that it’s easy to fix yourself, so you shouldn’t need to contact an engineer. To clear the blockage, you will need to thaw the pipe.

  1. Firstly, find the frozen section- it’s likely this will be at the outlet or at a bend.
  2. Using WARM water from your kettle or microwave in a jug or container- pour it along the frozen section of the pipe (DON’T use boiling water as this can damage the pipe).
  3. When you think that the blockage has been defrosted, try resetting your boiler by following the manufacturer’s instructions to see if the boiler starts and there are no error codes displayed.

If you still experience issues, contact a Gas Safe engineer for assistance.


How to prevent a frozen condensate pipe

When it comes to preventing your condensate from freezing again in the future, you have a couple of options. Your first option is to insulate the condensate pipe with waterproof lagging to prevent it from freezing. The next option would be to move the condensate pipe internally to ensure it stays around room temperature- a qualified Gas Safe engineer can advise further on this.



If you experience problems with your boiler and believe it to be due to a frozen condensate pipe, we hope that after reading this article you will be able to fix it yourself and get your heating and hot water back on in no time.

If you find that you’re still having issues with your boiler, or you do not feel confident following these instructions, we recommend that you contact a Gas Safe registered engineer for further advice.

If you would like to speak to a member of the Celsius team, just hit the button below to find out how you can get in touch with us.

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