DIY extension of Boiler Flue

29 Jan 2013
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United Kingdom
The exhaust plume from the central pipe section of my condensing boiler flue is continuously setting off the sensor of my outside security light.

The flue consists of 2 parts : first, a central pipe for expelling the boiler exhaust which extends beyond the 2nd part, an outer casing pipe housing the air intake to the boiler.

Would it cause any serious problems to the boiler if I attach a £4 L-shape waste pipe onto the central part (note NOT the air intake part) of the flue to route the exhaust plume vertically above and beyond the light sensor?

Note that this part is outside the house. No changes are being made to any other part of the flue, so there should be no risk of carbon monoxide or other dangerous gases getting back into the house, nor the boiler air intake being affected.

If the DIY L-shaped pipe will cause problems with the boiler, do I have to get an installer to extend the flue, or should I just buy a flue extension kit costing £80 and extend the flue vertically myself?


Should the installer have routed the flue above the light sensor when he installed the boiler?

N.B: The security light is a bit of a bother to move.
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It would be illegal, and dangerous. Don't try it.

A boiler man would be able to see if there's any flue extension he could add - it would have to be a boiler manufacturer's part.
Why would it be dangerous?

As I said, the DIY l-shape waste pipe is just extending the inner part thru which the exhaust flume is already exiting.

The exhaust is already outside the house.

The outer casing hence the air intake part of the flue is not being touched, so should continue to work as normal.
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Bit like saying I dont have a driving licence but know where the brake is so it must be safe for me to drive!

Even though I dont have any insurance!
I have uploaded an image of what the flue currently looks like, and the proposed DIY

Sorry as it seems I am unable to attach it to this reply


Should the installer have routed the flue above the light sensor when he installed the boiler?

And spent a whole extra 80 quid???
You've been told your way is dangerous and you can't do it.
What more do you want to know? :rolleyes: :rolleyes:
How hard can it be to move a security light a few inches? Waterproof connector, bit of cable and refit to wall in new position.
Why don't you try changing the sensitive of the PIR on outside light, you're able to do this on most of them or buy a replacement light that allows you to do this?

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