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frozen condensate pipe

How to Thaw a Frozen Condensate Pipe


A frozen condensate pipes can be a frequent occurrence for UK homeowners during the icy winter months. Finding your condensate pipe has frozen could leave you without heating and hot water. Ideally, you should have the condensate pipe thawed-out by an engineer, but if that’s not convenient then here are some easy guidelines to remedy the problem yourself.

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What is a boiler condensate pipe?

Modern condensing boilers have a condensate pipe which transports acidic water away from the boiler and down a drain. To improve efficiency, the boiler removes as much energy from the flue gases as possible and some of this waste gas cools and turns into a small amount of acidic water. The pipe transports this steady dribble of water away from the boiler and into a drain.

To check if your boiler has a condensate pipe, look at the pipes underneath the boiler entering and exiting the unit itself. If one of these pipes is plastic (usually white and around 20mm wide) and the rest are metal then you almost certainly have a condense pipe. Track the pipe to the outside of your home and you’ll find the pipe always runs to a drain so the water can be eradicated.

Why can condensate pipes freeze?

Because the pipe runs outside the home in order to reach an existing or its own drainage point, during the cold winter months the acidic water is prone to freeze. When it freezes in the pipe it creates a block so water fills up inside the boiler. A trigger is switched to shut down the boiler when it reaches a certain point to prevent the water flooding the entire system.

Where is the condensate pipe?

If you’ve found you’re condensate pipe frozen then you already know where it is. However, if a boiler error code has lead you to the conclusion that a frozen condensate pipe is preventing your heating from coming on then you’ll need to find it.

The condensate pip is a plastic pipe which leads outside with the open end being directly above a drain. Condensate pipes are never metal so checking the material of the pipe is the best way to know that you’ve found the condensate pipe.

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How thaw a frozen condensate pipe

It’s recommended that you have a qualified engineer come look at the condensate pipe, especially if you’re unsure of what to do or how to locate the frozen section. If you feel confident enough to attempt the task then there are two ways of thawing the pipe yourself.

  1. Apply hot water from a suitable container, like a watering can, to the outside of the pipe itself. Never use boiling water. If you don’t have running hot water due to the frozen condensate pipe then heat the water using a kettle or a microwave.

  2. Use either a hot water bottle or microwaveable heat pack and place it around the pipe at the section where the water has frozen.

You should never attempt to thaw a condensate pipe that is above ground level or disconnect the condensate pipe in the process.

You should employ extreme caution at all times when attempting to identify and thaw the condensate pipe.

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Frozen condensate error codes

To help you find the source of the problem when you’re left without central heating, modern boilers display an error code. Depending on the manufacturer, the error code will differ when there’s a frozen condensate pipe.

Boiler ManufacturerPossible Frozen Condensate Pipe Error Code
ATAG133
BaxiE133 or E28
Glow-wormF1, F4, F28 or F29
MainE133
PottertonE133
VaillantF28 or F29
ViessmannF4EE
Worcester BoschEA229 orD5

How to prevent condensate pipes from freezing

The Heating & Hotwater Industry Council (HHIC) advise operating the boiler at a higher flow temperature during the winter to reduce the amount of condensate forming, which will lower the chances of the condensate pipe freezing. This does mean that the radiators around your home will be hotter and your energy bills will rise so remember to turn the temperature on the thermostat down when the cold spell has passed.

In addition, the condensate pipe can be insulated to keep it warmer than freezing. To do this you’ll need a condensate freeze protection kit which can be added to the condensate pipe yourself or by a professional heating engineer.

Watch how to thaw a frozen condensate pipe

This useful video guide from Ideal shows you how you can safely defrost your condensate pipe quickly and effectively.

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