Thawing a Frozen Boiler Condensate Pipe

Frozen boiler condensate pipes can be a frequent occurrence for UK homeowners during the icy winter months. 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 try to remedy the problem yourself.

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What is the boiler condensate pipe?

Most modern boilers have a condensate pipe which transports water away from the boiler. To improve efficiency, the boiler removes as much energy from the flues 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 does have a condensate pipe, look underneath the boiler at the pipes entering and exiting the unit itself. If one of these pipes in 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 – you’ll find the pipe always runs to a drain so the water can be eradicated.

Why does it 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.

How do I clear it?

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. However, if you feel competenet enough to attempt the task then there are two ways of thawing the pipe yourself.

The first option is to apply hot water from a suitable container, like a watering can, to the outside of the pipe itself. Don’t use boiling water to do this. If you’re boiler is out of use because of the frozen condensate pipe you can heat the water using a kettle or a microwave.

The second suggestion is to use either a hot water bottle or a heat wrap – usually used to aid muscle discomfort and is available from all top chemists – 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.

Thawing a Frozen Boiler Condensate Pipe


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