When the ‘Beast from the East’ met the ‘Pest from the West’ in February and March 2018, many homes were affected by frozen condensate pipes, which meant their boilers shut down. This is a failsafe mechanism to protect the boiler from water going back up the pipe and inside the boiler, causing damage to the electrics.

It is quite simple to thaw the pipe and get your boiler up and running again. We explain how to do it below and advise how you can prevent it from freezing again.


How to tell if your condensate pipe is likely to freeze

Check to see if your condensate pipe runs along the outside of a wall at any point. The condensate pipe is a small, usually white, plastic pipe that comes out of the bottom of your boiler. It carries the ‘condensate’, which is the liquid produced when all the heat has been taken out of the gas that has burned to provide heating and hot water, to a drain.

Usually, the condensate pipe runs from the boiler to a drain under a sink, but in some cases, it may have been routed through the wall and into an external drain. The part of the pipe that is outside is most likely to freeze when temperatures start to plummet.

If your boiler is located in an unheated part of the house, for example in the garage or out-house, you should treat the condensate pipe as if it was outside. 

How to tell if the condensate pipe has frozen
In most cases, the boiler will display an error code. For example, on most Baxi boilers, the error code will be E133 or E28. The display will alternate between E1 and 33.  

How to thaw a frozen condensate pipe

  1. Locate the blockage. This is likely to be where the pipe is most exposed, outside the building and probably at its end or at a bend or dip in the pipe where the condensate could collect and freeze.
  2. Thaw the pipe. You can use a hot water bottle or a microwaveable heating pack (the sort used for muscular aches and pains) or a cloth soaked in hot water.  You can also pour hot, but NOT boiling, water onto the blockage, but remember that the water may freeze on the ground and make it slippery.
  3. Re-set or re-start the boiler. Once the blockage has cleared, check the boiler operating instructions or the manufacturer’s website for guidance on any action needed to clear the fault code or alarm and re-start the boiler. If it still doesn’t work, you should call a Gas Safe engineer to come and look at it for you. 


Please watch our video below that will help you thaw your frozen condensate pipe.



    How to thaw a frozen condensate pipe                                                                       

How to prevent the condensate pipe from freezing again

Once the pipe is thawed and the boiler has been successfully re-started, you can lag the pipe with waterproof and weatherproof lagging to help prevent it re-freezing.

As a temporary measure, it may help to turn the boiler thermostat (not the room thermostat) to maximum and run the boiler in ‘continuous’ mode, turning the room thermostat to 15°C at night.  Turn back to the normal settings once the cold spell is over.

In the longer term, in order to prevent the pipe freezing again, you can ask your Gas Safe registered installer to move the pipe so that it runs internally.  Alternatively you could ask them fit a wider pipe, lag it to reduce the risk of freezing, install a trace heater along the pipe which warms it slightly when temperatures drop to freezing, or a combination of all of these.

Please watch our video on how to prevent frozen condensate pipes.



    How to prevent the condensate pipe from freezing again                                     

British Standards, Building Regulations and boiler manufacturers’ instructions all provide information and recommendations that can advise your installer on how to run the pipe to reduce the risk of freezing.


Condensate pipe installation is also included in the Benchmark checklist that your installer should go through with you when he has completed your boiler installation.


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