How to Thaw a Frozen Boiler Condensate Pipe

What is a condensate pipe?

A condensate pipe is an additional pipe that is fitted to carry away waste water from a condensing boiler. It is normally a piece of plastic and it runs from the boiler to a household drainage pipe or soakaway outside. 

Evidence of condensed water running through the pipe is an indication that your boiler is working as it should be. Long periods of cold weather can cause the pipe to freeze, affecting the operation of the boiler.

Where is the boiler condensate pipe?

The condensate pipe runs from the boiler to an appropriate existing waste pipe  or external pipe. You will be able to see the condensate pipe underneath your boiler, and it should be the only plastic pipe visible. 

If your condensate pipe is connected to an external drain pipe, it will be found outside your property leading from your boiler. 

How to tell if condensate pipe is frozen

If your condensate pipe is frozen, you may hear gurgling noises coming from your heating system, and the boiler may shut down.

This is a failsafe mechanism to protect the boiler from water going back up the pipe and inside the boiler, which could cause damage to the electrics.

How to thaw a frozen boiler condensate pipe

If your condensate pipe has frozen, you shouldn’t worry. It can be sorted in a few steps likely without having to contact a heating engineer. 

Before you start, you should first find the blocked part of the pipe. This way, you can be sure you’re thawing out the right part of the pipe. Most blockages occur if there’s a bend or dip in the pipe. 

You can unfreeze the pipe in one of two ways:

• You can hold a hot water bottle, heating pack or warm cloth around the frozen part of the pipe, or; 
• You can pour hot water over the frozen area. Make sure you don’t use boiling water as this can cause the plastic pipe to melt.

After you’ve unfroze the pipe, you might need to reset your boiler. Some boilers may do this automatically, so it’s a good idea to check your boilers manual for the next steps. If you don’t feel comfortable unfreezing the condensate pipe yourself, you should always get in touch with a qualified heating engineer for expert help.

If you are really struggling to defrost the pipe a heating engineer can attend and cut the pipe as a temporary measure. It would then need to be reconnected when the temperatures increase.

How to prevent a boiler condensate pipe from freezing again

There are a few ways you can prevent your condensate pipe from freezing again. Firstly, you should take the following steps into account as the colder months approach:

• Use foam pipe insulation to cover the condensate pipe.
• Consider having your condense pipe upgraded to a larger bore pipe, If you have an older installation it will be a smaller diameter. 

If you have a Worcester Bosch boiler, they have a CondenseSure device which can be fitted to prevent boilers from freezing in temperatures as low as -15°C.  

Unfortunately, sometimes, when the temperatures are extremely low for prolonged periods there’s not much that can be done to completely prevent a pipe freezing, but at least you can be aware of what it is and how to deal with it.