If you’ve noticed that your boiler has stopped working and it’s cold outside, it could be that your condensate pipe has frozen, and that should be one of the first things you check out.

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Your boiler’s condensate pipe runs right into a drain, and can usually be found outside of your home. Which is why it is so often prone to freezing.

A frozen condensate pipe is usually the result of ice or other debris getting into the pipe and freezing, thus blocking it so that it cannot do its job. When your condensate pipe cannot do its job, your boiler shuts down to ensure you and your family are kept safe.


A quick guide to thawing your condensate pipe

Step one

Find your condensate pipe. It should be a white pipe that protrudes from the portion of the wall that is located directly behind your boiler. You’ll know you have the right pipe if it runs right out from the boiler to an exterior drain.

Step two

Boil your kettle and let the water cool for approximately 15 minutes — you want the water to be warm rather than boiling hot. Starting at the top of the kettle and making your way down the pipe, pour the warm water over your frozen condensate pipe until the ice blocking it has thawed.

Step three

Reset your boiler. Wait a few minutes and check that is working properly. If you have fully thawed your frozen condensate pipe, everything should be working as normal. 


How to prevent a frozen condensate pipe

Now that you have thawed your frozen condensate pipe, you’re going to want to make sure that it doesn’t happen again. In order to do that, you’re going to want to follow our preventative tips:

Install a large pipe

The best way to lower your chances of having to deal with another frozen condensate pipe is to install a pipe that is as large as possible. Before doing this, you should take a look at the manufacturer’s instructions to see what they recommend. Usually, manufacturer’s will recommend pipes in the range of 32-40mm, but it is possible to have an engineer install a thicker pipe if you have to deal with extremely cool temperatures, where thinner pipes might not cut it.

Add insulation

Insulating your condensate pipe will help to protect it from the elements. It’ll be kept warmer, which means that it will be far less likely to end up frozen.

In order to insulate your boiler condensate pipe, simply wrap with foam pipe insulation and secure with strong tape or cable ties.

Reduce external piping

It stands to reason that the less condensate pipe you have on the outside of your home, the less opportunity there is for your pipes to freeze over. So, if it is possible for you to do so, you might want to move the pipes to minimise exposure to the elements. Usually, you will need to call a heating engineer to help you with this.

Reduce exposure

Placing your condensate pipe in the optimum position so that it gets plenty of sun and isn’t particularly exposed to the elements is a good way to minimise the risk of freezing.


Ensuring that waste falls from your pipe as quickly, and from as great a height as possible will help to keep the pipe clear so that it is unlikely to become blocked. Ensuring that your pips have as few bends as possible will also help to this end.

Get a siphon trap

If you’re in the process of purchasing a new boiler, try to choose one that features a siphon trap. This is a type of condensate release that flushes out the water in one go, thus lowering the risk of freezing. The majority of boilers release the water in long drawn our drips, which means there is more water present for longer, making it more likely that a freeze will occur.


A trace is an electrical element that can be bonded to the area below your condensate pipe. It is able to warm the pipe when the temperature drops below 5°C. If you install it, you must also add lagging to the pipe to ensure that it is insulated. If you live in an area where temperatures regularly drop below 0°C for a prolonged period of time, this could be a useful addition to your boiler setup because it really is the only way that you can guarantee your pipe will not freeze. 

It should be noted that the only way to add a trace to your boiler condensate pipe is by calling a Gas-Safe engineer to do the job for you.

With a few changes and a little ingenuity, you can thaw frozen condensate pipes and prevent them from freezing again.



We hope this guide has helped you with your heating. If you’re interested in pursuing a career as a heating engineer, you can find out further information here. We also have a range of plumbing courses aimed at both experienced engineers and new entrants.

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