How to thaw a condensate pipe


Has your boiler stopped working? If it’s happened after a particularly cold night, don’t panic—your condensate pipe may just be frozen.
How to thaw a condensate pipe

Has your boiler stopped working overnight?

If it happens after a freezing night, don’t panic—your condensate pipe may be frozen.

And if that’s the case, it might be time to put the kettle on…

From locating the blockage to restarting your boiler, we grilled our Home Experts on how to sort out the problem and get your home warm again in no time.

What is a condensate pipe?

A condensate pipe carries condensation from your boiler to your outside drain.

It’s usually a white or grey plastic pipe that travels from your boiler through the wall directly outside where your boiler is located.

During cold weather, the condensation in this pipe may freeze and cause a blockage causing the condensation to back up into the boiler and cause it to shut down.

How to defrost or thaw a condensate pipe 

Even if you take the utmost care of your boiler, it will struggle to function if its condensate pipe freezes. 

In our blog below, one of our Home Experts, explains exactly how to thaw a condensate pipe safely.

Check out our handy step-by-step guide below

Step 1: Confirm the condensate pipe is frozen

Depending on the make and model of your boiler, a frozen condensate pipe may be indicated by a ‘fault code’ or warning light on the boiler’s display.

Gurgling or bubbling sounds coming from the boiler or the condensate pipe is another sign that the condensate pipe has frozen.

Step 2: Locate the blockage

The pipe is probably frozen at its most exposed point.

This may be the open end of the pipe, or at a bend or elbow.

Running your hands over the pipe until you find a section that feels colder than the rest should help you identify the blockage quickly.

Most condensate pipes freeze near the ground, so it’s simply a case of pouring the hot water over the pipe slowly.

Step 3: Use hot water to thaw the pipe

First, boil some water. If you’re using a kettle, make sure to cool the kettle for at least 15 minutes once it’s boiled.

Do not use boiling water as this can crack or damage the pipe.

Using a jug or watering can pour hot water along the length of the pipe, repeating the process until the pipe has thawed.

Be careful where you pour the water—it may freeze and become a slip hazard.

Alternatively, you can use a hot water bottle or a heat pack to slowly defrost the condensate pipe.

Step 4: Restart your boiler

Once the frozen section has been melted and cleared, check your boiler manual for instructions on how to reset the boiler correctly. Your boiler should now restart.

Step 5: Not fixed? Keep trying

It may take several attempts before your boiler restarts, but if it doesn’t, you may need to call out a qualified boiler engineer.

How to stop your condensate pipe from freezing

It’s easy to thaw your condensate pipe once it has frozen, but it’s better to prevent your pipes from freezing in the first place.

We asked Home Expert for tips on how to stop your condensate pipe from freezing and save you the hassle of waking up to no hot water.

Wrap it in some old towels

If your condensate pipe isn’t already insulated, wrap it in some old towels immediately to prevent it from freezing.

Get foam pipe insulation 

As soon as you can, get down to your local DIY store and buy some foam pipe insulation to wrap the condensate pipe in (just make sure to check it’s for external use).

This insulation comes in a variety of sizes, so measure the pipe’s diameter before you buy.

Turn up the heat! 

During extreme weather conditions, even proper insulation may not be enough to prevent the condensate pipe from freezing.

It may help to temporarily run your boiler with the boiler thermostat set as high as possible for as long as the cold spell lasts.

But if you continue to experience problems, it’s best to call out a qualified boiler engineer for help.

Cover your drain opening

Add a leaf guard over the open end of your drain to remove any wind chill.

This will reduce the chance the water in your condensation pipe is exposed to sudden drops in temperature—meaning it’s less likely to freeze.

Boiler still not working?

If you’ve followed our advice on how to thaw a condensate pipe but your boiler still isn’t working, try diagnosing your central heating problems.

Alternatively, you may need to call out a qualified boiler engineer.

PlusHeat’s nationwide network of gas-safe engineers is here to help.

Simply get in touch, safe in the knowledge you can count on us to keep you feeling toasty this winter.