How to defrost a frozen boiler condensate pipe

If your heating stops working in sub-zero weather, it could be down to a frozen condensate pipe. This can happen even with a well-maintained boiler on icy days. But luckily it’s something you can usually fix at home.

Read on to find out if your condensate pipe has frozen, and how you can thaw it and get your heating working again. You’ll discover what not to do so you don’t damage your boiler, and find out how to stop it happening again in future.

How to know if your condensate pipe is frozen

Unless you have a really old boiler, it’s likely that yours has a condensate pipe. This is the case whatever brand of gas boiler you have – whether it’s Worcester, Bosch, Vaillant, Viessmann or any other brand. If you’re not sure if you have a condensing boiler, find out more in our handy guide to the types of boiler available.

First, find your condensate pipe

Your condensate pipe might have frozen because it runs outside or into an unheated space, like a garage. If it runs outside, it’s usually channelled into a soil or rainwater pipe, gully, or soakaway. It will be plastic, while your other boiler pipes will be copper or steel. This is because it gets rid of the excess condensation created by your boiler, and the water going through the pipe is mildly acidic. The acid would corrode a metal pipe.

Signs your condensate pipe is frozen

Here are the key signs:

• Your heating’s stopped working.
• Your boiler’s making a gurgling or slurping sound.
• Your boiler display’s showing an error code that indicates a problem with the condensate pipe. (See the bottom of this article for more on common condensate pipe error codes).

Defrosting your frozen condensate pipe: a quick guide

Once you’ve realised you have a frozen condensate pipe, you’ll want to unfreeze it.

1. Work out which part of the pipe is frozen
   Run your fingers along the pipe – the part that feels coldest is probably the frozen part.

2. Boil your kettle
   Then wait for 10-15 minutes to let the water cool down. It’s important never to use water that’s just boiled, as it could crack the pipe and cause more damage.

3. Pour the warm water onto your pipe
   You can either do this along the whole length of the exposed pipe, or just on the spot that’s frozen (if you know where that is). The warm water should melt the icy blockage.

4. Reset your boiler
   Once you’ve done this, reset your boiler to see if the problem’s been solved. If it has, your heating should start up. If not, it might be worth trying again.

After a few attempts, if the heating’s still not working, you should call a professional to take a look. If you have CORGI HomePlan cover, you can contact us online or call 0330 102 8256.

How to stop your condensate pipe freezing

Here are some ideas to make sure the pipe doesn’t freeze again:

• Insulate the pipe
  Temporarily wrap it in some old towels or blankets, while you head to your local DIY shop to pick up some foam pipe insulation (make sure you measure how thick your pipe is first). This can help protect your pipe in future. If your pipe’s difficult to access, a professional can do it for you.

• Change the condensate pipe’s position
  The less pipe that’s outside, the less it can freeze in cold weather. To change the location of your condensate pipe, you’ll have to call an engineer.

• Change the angle of the pipe
  Pipes that point downwards steeply mean water can drain properly, so they’re less likely to get water trapped inside them that then freezes. Your pipe’s also more likely to freeze if it has lots of bends. You can change the angle or the bends of your pipe, but you’ll need the help of a professional.

• Ask your plumber about installing a trace
  If you live somewhere that often gets very cold, you might need to ask your boiler installer about fitting a trace. This is an electrical element fitted to your pipe that heats it up when the temperature drops.

Frozen condensate pipe error codes

These error codes are used by the most common boiler brands to show that the condensate pipe’s frozen. If your boiler’s showing a different error code, check your boiler manual.

Make of boiler	Frozen condensate pipe error code
Baxi	E133 or E28
Glow-worm	F1, F4, F28 or F29
Ideal	LF, F2 or L2
Vaillant	F28 or F29
Viessmann	F4
Vokera	92, 93 or 95
Worcester Bosch	EA229 or D5

What if your boiler condensate pipe isn’t frozen?

If you’re not seeing any of these error codes, or the signs of a frozen pipe listed above, it could be a different problem. You might need to top up the pressure on your boiler, or bleed your radiators. Check out our help hub for advice on how to solve common boiler problems. If you’ve tried everything above and your boiler’s still playing up, you might need to call an engineer to get it running again.

Signs of a serious problem

If your pilot light often blows out, or there are sooty stains around your gas appliances, you could have a carbon monoxide leak. Carbon monoxide poisoning is lethal. Always call a professional immediately if you spot any of these signs.

Protect your boiler with CORGI HomePlan cover

While we don’t cover frozen condensate pipes, with CORGI HomePlan, you’re covered if your heating stops working for another reason – or your boiler has any issues¹. Our plans start from just £15 a month. They include boiler and central heating cover, and an annual boiler service to help keep things running smoothly.

1. Terms apply.