# Galv. duct pipe



## tlr (Sep 27, 2010)

I wanted to post this in several places to get an answer, I did a search but it didnt answer speciffically…
I was at lowes today pricing PVC and galv. duct pipe and the duct pipe is far cheaper, has the of PVC gone up? 
Also is there any down side of using the galvanized duct pipe for the main runs?


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## 33706 (Mar 5, 2008)

tlr asks, "I wanted to post this in several places to get an answer, I did a search but it didnt answer speciffically…
I was at lowes today pricing PVC and galv. duct pipe and the duct pipe is far cheaper, has the of PVC gone up? 
Also is there any down side of using the galvanized duct pipe for the main runs?"

Main runs of what, the flue to your wood stove? I'd go with galvanized….


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## GMman (Apr 11, 2008)

A PVC flue on a wood stove???


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## tlr (Sep 27, 2010)

sorry sorry, i am trying to do to many things at the same time, i posted under the dust collection thread first. 
I was looking at 6" galv. pipe for my main run of DUST COLLECTION then trying to get as close to each machine before going down in size for the machine fittings. i.e. 6-4", 6-2.5" etc. so the question is, is there a down side to galv. heating duct pipe for dust collecting? it is far cheaper than the "spiral" and other metal stuff that I have seen and it is cheaper than the PVC that I saw today.


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## tlr (Sep 27, 2010)

So outside of additional cost of fittings and making sure it is at least 26 gauge I sould be fine?! Sonds good to me, I almost choked on the cost of the other metal pipe specifically made for dust collection and such. I am sure it is a bit nicer stuff but if it fits the bill why not?


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## tlr (Sep 27, 2010)

Thanks I was thinking that myself…the stuff they use when putting together normal joints for household stuff correct?


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## brtech (May 26, 2010)

The foil tape I'm used to does not have as an aggressive adhesive as most duct tape, but YMMV. It does look nice though! Its much more expensive.

tlr make sure you are comparing 26 ga metal duct to S&D PVC. PVC pricing has gone up some, but I'm surprised it's more than metal duct. I'll have to check it out myself.

Don't forget that you need Y's, not T's for the branches, and you want two 45 degree elbows with a section of straight pipe between them, not 90 degree elbows to change direction.

Blast gates really are necessary for a permanent install.


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## oldworld124 (Mar 2, 2008)

The thin galvanized duct pipe will have a good chance of collapsing if you use it for dust collection. You can get by using what is called S&D drain pipe for up to 6" runs. For metal it will be best to use spiral pipe. It is specifically designed to be rigid and light. Costs a bit more but well worth it. The bends MUST also be soft. Never use tight bends for duct work. Also, try to keep the plastic flex duct as short as possible. You will loose a lot of vacuum efficiency if the flex is too long.


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## patron (Apr 2, 2009)

here's what i did
i used it all the way thru
but had to go the hd and lowes for the fittings
the tees are not the best
so look them over
they both carry different brands
i was worried about collapse too
so i didn't tape the joints
might lose some suction
but they haven't collapsed yet
even with all the gates closed
i had to rig some things
but overall i saved money
so it is worth it

the thing sucks lol


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## KnotWright (Nov 6, 2008)

For me I went down to my local HVAC supply house and bought my fittings and snap lock piping. David (patron) that's an impressive layout you've got there! Wish mine looked as nice, but with 14 foot ceilings, I opted to run mine low, so I have more obstacles to work around.

I even had the supply house make me up some custom reducers to make hooking up the hoses to the machines easier.


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## Finn (May 26, 2010)

When I was working at sheetmetal work we did a smoke test on spiral pipe. I was surprised to learn that it leaks badly all along the spiral seam ! Snap lock pipe also leaks but can easly be sealed with tape, caulk, or solder.


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## Chriskmb5150 (Dec 23, 2009)

I've never had a DC in my shop but im an HVAC mechanic by trade and have worked with quite a few dust collection systems both large and small (large being 400hp and small being 15 - 20hp).
I would advise AGAINST using plastic pipe for DC purely to avoid static electricity build up.
I've seen ABS pipe hold a charge like a capacitor and discharge *thru me* to ground.
We tried grounding with copper wires in and out of the pipe and it really doesnt work.
If anyone here has a DC system with plastic pipe and youre not having static problems consider yourself lucky imo.
Snap lock pipe would probably be ok for a small system if you seal all the seams with mastic and screw or rivet the longitudinal seams so they dont implode. 
point the crimped ends downstream to avoid buildup. 
Keep the duct as small as possible to keep the velocity high. (we usually size our ducts for no less than 3500fpm velocity)
Avoid using long screws to fasten the joints. instead, use rivets.
I would also recommend spiral duct but it is pricey.
I'm gonna probably use spiral pipe for my DC whenever i get around to it but i have access to free scrap pipe and can make the fittings myself.


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## snowdog (Jul 1, 2007)

I have PVC drain pipe and it works fine, never got a shock. Much less expensive and works great. In a professional shop I would go with what the insurance companies would approve in case of accident but for personal use, PVC is for me


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