# Metal DC ducting?



## GISer3546 (Jan 30, 2013)

Poking around at my nearest big box store I saw these:

http://www.homedepot.com/p/Master-Flow-4-in-x-5-ft-Round-Metal-Duct-Pipe-CP4X60/100196725

They're significantly cheaper than any PVC or hose I've seen used in a DC system, but I've never seen them in use anywhere. I'm assuming there just has to be some reason why I can't route these guys through my rafters for my DC... but I can't think of any. If I were to seal the joints with metal ducting tape would I still end up with issues that make the extra cash for PVC worth it?


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## jdonhowe (Jul 25, 2014)

Those ducts are 30 gauge- they have a good chance of collapsing in a DC system. I vaguely recall, though, somebody who reinforced his ducts (thin- don't remember gauge) with wooden rings- helped keep them circular and more resistant to collapse.

Also, I don't think this is any cheaper than PVC- this is for 5'; PVC is for 10'. You might also want to check out triple wall HDPE drain pipe at HD- $9.51/10'


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## ryan50hrl (Jun 30, 2012)

I would love to see a test of that collapsing with a 2-3 hp dust collector. It's not that I don't believe you, but my father in law used a flexible dryer vent on his 1 hp dust collector and it didn't collapse, just eventually got a bunch of holes in it. I would suspect that regular ol steel dryer vent would hold up fine.


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## WarnerConstInc. (Nov 25, 2008)

I have a mix of spiral DC pipe and 26 ga hvac pipes and fittings. i am running a grossly over rated 5hp DC. 

They work fine, just tape all the seams.


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## hwebb99 (Nov 27, 2012)

I'd buy one piece. Tape one end, and see if your dust collector will crush it. If not just for the fun of it try your shop vac.


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## Steve Neul (Sep 2, 2011)

From what I understand the metal ductwork is easier to ground to cut down on static electricity.


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## Leo G (Oct 16, 2006)

If you are running a 2HP+ DC make sure it's 26ga or thicker.


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## jdonhowe (Jul 25, 2014)

Okay, a clarification. I found the posting I remmbered- it's on another ww forum- not sure about rules here re: links to other sites, so Google "30 gage metal duct pipe can collapse". (poster doesn't know how to spell gauge  ).

He had a Jet 1900 3hp DC, and had duct collapse with closed blast gates. He retested, and instead of aligning the seams, he oriented seams of adjacent sections 90 degrees apart, and got no collapse. Probably worth checking out the thread.

So, I recant my earlier post. Sorry for the misinformation.:surrender:


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## epicfail48 (Mar 27, 2014)

Just checked and norfab uses 20 gauge sheet for their ducting systems, so 30 seems a little light to me. Id imagine that the vacuum from a DC would crush that thinner stuff in a heartbeat


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## ryan50hrl (Jun 30, 2012)

Norfab also isn't creating ducting for a 2 hp hobby shop dust collector. 

Anyone that hasn't tried it yet, get a piece of it, tape the seams and try to collapse it applying uniform pressure around its edges....it's going to take a lot more than you'd think.


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## CrazyHorse (Dec 19, 2014)

PVC is cheaper all around. You don't have to seal seams like you would with metal ducts, and fittings work better. Metal elbows will create friction loss, and you have to seal the dickens out of it.

There is no reason to ground dust collection in a home hobby shop.


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## ryan50hrl (Jun 30, 2012)

The reason to ground in a hobby shop is it hurts less. My planner chips running through 10 feet of flex tube create enough static to hurt...

Now...I'm not saying PVC isn't a good choice, I'd probably use it myself....but there's nothing inherently wrong with snap lock steel duct. Seams and joints seal very quickly with aluminum tape.


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## Steve Neul (Sep 2, 2011)

I think if someone wanted to use the 30 ga. pipe it could be re-enforced to keep if from collapsing. It might be enough to put it through a short piece of schedule 40 pvc pipe about the middle and glue it to the metal pipe.


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## GISer3546 (Jan 30, 2013)

appreciate it guys, It seems like the metal isn't quite offering the savings I thought, and not having to worry about sealing seams sounds like a plus. If I end up going with metal I'll be sure to find something well thicker than 30 ga.


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## Carvel Loafer (Dec 31, 2011)

The last shop I worked in with a DC used metal spiral pipe. I don't recall the gauge but being spiral it was pretty tough. The flex pipe we used was a heavy black fabric reinforced with a spiral wire. Everything was grounded including the flex pipe and we never had a spark. I forget the size of the unit but if all the gates were closed it would never even hint at collapsing.


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