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Preventing condensate pipe freezing while away from home

Postby snaj » Sat Dec 04, 2010 11:05 am

Hi All,

Like many others, I've had the problem of overnight freezing of the external condensate pipe on a combi boiler, despite the lagging. I've been thawing it as necessary. However, I am soon going to be away for about 3 weeks, so I'm a pretty concerned about what might happen. Is it possible for the condensate pipe to freeze even when the boiler is running? If not, would it be best for me to leave the boiler running constantly (i.e. 24 hours a day) at a fairly low temperature for the time that I am away?

All advice will be very welcome.

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Postby steve61 » Sat Dec 04, 2010 10:16 pm

"Is it possible for the condensate pipe to freeze even when the boiler is running?"


If you are going away why not turn off the boiler until you return.

I get the same problem and have to unfreeze the pipe almost every day in sub-zero temperatures.

Steve :D
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Postby htg engineer » Sun Dec 05, 2010 7:32 pm

Any external pipework should be 1.25" diameter, does the condensate discharge into a gutter or gully that is full of snow ? cut the pipe back so that if the gully/gutter fills with snow - it will not block the condensate pipe.

If the external pipe is 22mm then that's the problem - increase pipe size to 1.25"

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Postby snaj » Tue Dec 07, 2010 12:56 pm

Thanks htg engineer - the pipe discharges directly into the main soil pipe, and none of that is exposed, so there shouldn't be any snow blockages. I hadn't checked the diameter of the pipe, but its a relatively new install, by British Gas. Am I naive to think that they would have done the right thing??

Thanks steve 61 - if I shut down the boiler, I would also have to drain down the system to avoid frozen/burst pipes, and I was keen to avoid the need to do so.
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Postby angelpie » Fri Dec 10, 2010 4:36 pm

i have a worchester bosch boiler, and the white narrow condensing pipe that leads out of the bottom of it is about a meter long, it then pushes into a 40ml pipe which leads outside to the drain, which like many it is freezing over in low temps. my question is does this white pipe have to be this long, can i cut it down and lenghen the 40ml pipe.

hope someone understands what i'm trying to explain, any advice will be great
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