Metal furnace ducting for mainline???????????????

Question

Hi group:What success have you people had using the normal household furnaceducting for a mainline.  I know I would have to duct-tape the joint onthe whole length??????????????Jow-->  Remove par from email address for replying

Dave W · Accepted Answer

Part of my system uses 30ga ducting. Works fine!

billh · Answer

I have heard of some saying their system can collapse the thin stuff if all their gates are closed but I have my doubts unless their system is extremely tight and have some damaged duct (badly flattened). If you think you are approaching this situation just bleed a bit of air - yeah, I know that isn't the idea but life isn't perfect at least on the cheap.Billh

cr480 · Answer

Good success in my situation, which is a part time shop using a DC1100C with1 to 2 machines at a time, mostly 30 Ga round 4" (some 26 Ga), standardadjustable Ell's, going two directions with the DC in the middle.  Thesestandard Ell's won't hold up to the wearing action of wood particles 40hours a week of course, but then again, replacing a $6 Ell once in a whileisn't a big deal either.  I either used metal duct tape or gray RTV for thejoints from one pipe to another or to a fitting, and mostly ignored the seamdown the length of the pipe.  A main trunk of 5" round would have been ok orbetter when multiple gates are open, but if I had to do it again, I'd savethe few $ and use 4" again.  The 45 degree wye's are better than 90 degreeTee's.  Grounding is so easy with this stuff, and there are no ground wiresin the pipe to catch clogs.There are a number of sites on the web that descibe some of this like: and

Dr. deb · Answer

You can also use 4" schedule 40 PVC.Deb

Bruce · Answer

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I use metal, too. The only problem I see with the PVC is that you still have to ground it, whereas the metal acts as a ground.

"Just one OLD man's opinion."

The Other Bruce

J. Clarke · Answer

The problem with "just bleed a little air" is that you don't know you needto until it's too late.

Ken Moon · Answer

SNIP ....====================Bruce,The metal ducting is conductive, but is not grounded unless it is in contactwith a grounded tool, or has a grounding wire run to an established groundlug/connection.Ken MoonWebberville, TX

Glen Duff · Answer

Jow,I installed some in my shop about 5 years ago and it seems to work fine, also it's pretty cheap.  However, I put one length of a heavier duct called spiral duct that has a length of steel curled around the outside.   It is much more substantial and if the cost isn't critical I would definitely recommend this instead.Good luck,Glen Duffgolf wrote:

Metal furnace ducting for mainline???????????????

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