Cutting Double Wall Pipe

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MongoMongoson

Member
Feb 6, 2021
215
Wisconsin
In another thread where I gave instructions on how to cut double wall pipe, bholler let me know this is not OK. Thank you for that. It never occurred to me that I would not be able to cut it to length.

This seems like another one of those things that does not make a lot of sense. When I did it, I needed a section that was more than 18 but less than 24. I had a 12-18 adjustable section and an 18" section leftover that I had dropped on the concrete and smashed the end that I eventually cut off.

So, I either run to the store to get a 6" section or cut what I already had. It fit together wonderfully snug after I cut and crimped it... much better than the factory fit. I know that doesn't matter when it comes to code.

Is there a reason I am missing that makes this a bad idea (unsafe in any way) and should I bother to swap it out with a 6" section next time I take the pipes apart?

The homemade section is part of the 45 run in this picture.

20210318_160946.jpg
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,199
central pa
In another thread where I gave instructions on how to cut double wall pipe, bholler let me know this is not OK. Thank you for that. It never occurred to me that I would not be able to cut it to length.

This seems like another one of those things that does not make a lot of sense. When I did it, I needed a section that was more than 18 but less than 24. I had a 12-18 adjustable section and an 18" section leftover that I had dropped on the concrete and smashed the end that I eventually cut off.

So, I either run to the store to get a 6" section or cut what I already had. It fit together wonderfully snug after I cut and crimped it... much better than the factory fit. I know that doesn't matter when it comes to code.

Is there a reason I am missing that makes this a bad idea (unsafe in any way) and should I bother to swap it out with a 6" section next time I take the pipes apart?

The homemade section is part of the 45 run in this picture.

View attachment 276675
It could certainly be done without compromising safety at all. But it is a ul listed product that says you can't cut it in the directions. That means once you do that the listing is void and so are the clearance specs legally speaking.
 

MongoMongoson

Member
Feb 6, 2021
215
Wisconsin
I understand now. The Selkirk instructions don't specifically say you can't cut it. But, as far as UL is concerned, it should be installed in the form in which it was tested. The only way I could cut it is if the instructions said I could cut it to length.

The Selkirk instructions leave a lot to the imagination, meaning they don't really provide a heck of a lot of information considering how critically important it is to install it correctly.

I will leave it in place for now, and when I take the pipes apart next time I will "fix" it. Not sure when that will be, since I have started using a soot eater for sweeping.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,199
central pa
I understand now. The Selkirk instructions don't specifically say you can't cut it. But, as far as UL is concerned, it should be installed in the form in which it was tested. The only way I could cut it is if the instructions said I could cut it to length.

The Selkirk instructions leave a lot to the imagination, meaning they don't really provide a heck of a lot of information considering how critically important it is to install it correctly.

I will leave it in place for now, and when I take the pipes apart next time I will "fix" it. Not sure when that will be, since I have started using a soot eater for sweeping.
I really doubt there is any safety risk but modifying ul listed products unless instructions allow for it can be risky
 

Shrewboy

New Member
Oct 15, 2020
82
Eastern Pennsylvania
I used an angle grinder to cut the final piece of double wall telescoping pipe to be able to fit (it was slightly too long)

I used 2 x 45 elbows like begreen said instead of a 90 :D! but by doing that it created the situation where the telescope wouldn't slide down enough to make it fit.

I looked online and couldn't find a pipe that would fit in the required spot, maybe I should have looked harder lol oh well