Preventing and Thawing Frozen Condensate Pipes

With the UK suffering from bitterly cold winter temperatures, Hassle Free Boilers want to provide you with some simple and helpful advice to ensure you get the most from your boiler and heating system.

Your boiler condensate discharge pipe may be at risk of freezing in prolonged, and extreme cold weather conditions and in recent years we have seen temperatures as low as -20°c in some parts of the UK. The concern is that if your pipe runs externally, or in an unheated space for at least some of its length and is liable to freeze in these extreme temperatures as it is not installed in line with the latest guidance, it needs help to guard against freezing. If your pipe freezes, it will cause your boiler to go into “shut off” at a time when you need your heating and hot water the most.

Here is a checklist of what you can do to prevent and thaw your condensate pipes if they freeze this winter.


If appropriate, it may be advisable to operate the boiler temperature at a higher flow temperature as this would decrease the amount of condensate generated and reduce the freezing potential during the cold spell. This is achieved by turning the boiler thermostats to a high setting. During this situation the radiator surfaces will be hotter than normal and the boiler efficiency will be slightly reduced.

Remember to return the boiler thermostat back to its normal position after the extreme cold spell has ended.


1. Locate the blockage

The condensate discharge pipe usually freezes at the most exposed points outside, such as the open end of the pipe, at a bend or elbow, or where there is a dip in the pipe where condensate can collect.

2. Thaw the frozen pipe

The condensate can be thawed in a number of ways. By applying a hot water bottle or microwaveable heat packs around the blockage or by pouring warm water onto the pipe. It is important that you do not use boiling water.

Please take care if your condensate discharge pipe is not easily reached from ground level and do not put yourself at any undue risk without seeking assistance or engaging a professional heating engineer (please get in contact if you need help) – also be aware that if you are pouring water onto the pipe this can also quickly freeze on the ground, causing a slip hazard.

3. Reset / restart the boiler

Once the frozen blockage has been cleared, the boiler will usually need to be reset, and advice on how to do this can be found in the user instructions manual for your boiler. Normally this will involve simply pressing a reset button on the front of the boiler, or in some cases by isolating the electrical supply to the boiler and switching it back on.

4. Book your annual service

Give your boiler some love and care by ensuring it is serviced it each year to maintain its efficiency and prevent breakdown. Call us today on 0800 111 40 40 to arrange.

Stay safe and stay warm!

Kind Regards
The Hassle Free Boiler Team

Guidance provided by The Heating and Hotwater Industry Council (HHIC). Please get in touch with us today if you need assistance.

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