How to thaw a frozen boiler condensate pipe

If the condensate pipe has frozen, you may hear gurgling noises coming from your heating system, and the boiler will 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 etc.


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.


It is simple to defrost your condensate pipe and you shouldn’t need to call your heating engineer. Please wrap up warm and take care not to slip on the frozen ground.


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.