With the cold snap we are experiencing, some of you will have found your boiler has inexplicably stopped working. There may even be a fault code showing as you scan through your boiler manual trying to establish what can be done to remedy the situation. Chances are you have a condensing boiler, which more than likely will have a frozen condensate pipe.
More often than not, this pipe will be white plastic, around 22mm in diameter and if it passes through an external wall to the outside there is every likelihood that the condensate created by the boiler has frozen, preventing it from being able to drain safely away. Sensing this, most boilers will eventually shut down after trying to ignite around five times, thus showing a fault code – but it is most unlikely your fault code will show as blocked or frozen condensate drain.
The remedy is surprisingly simple, first locate where the pipe exits the building, even if it is joined by a much larger piece of waste pipe. Then carefully carefully apply heat by pouring very warm water (not boiling hot in case it shatters the pipe or deforms it) over the pipe as shown in the picture below, this might take a couple of applications. By doing this you should be able to melt the frozen condensate which has formed a plug in the pipe; start first at the point of exit from the building, especially as there is going to normally be an elbow there.
Once you have managed to clear the frozen section, it would be advisable to fit pipe insulation around the condensate pipe to help prevent this from occurring again. For the record, the pipe should actually be at least 32mm diameter when run outside the building fabric, better still if it can be run internally. It is considered bad practice to use 22mm externally and any upsizing from 22mm to 32mm should actually be made internally rather than externally.
Once you are satisfied or confident that you have melted the frozen blockage, reset the boiler according to your operating instructions and all should be well. You may need to repeat this if it doesn’t work the first time.