# Ductwork Help



## Ken Johnson (Nov 8, 2007)

I recently purchased a Grizzly 3HP dust collector (2340 CFM) and I have run a metal spiral 6" main duct down the center of my shop which I got for free along with many other elbows and connectors. I need to run about ten 4" lines off of that to all my different pieces of equipment with blast gates. However I recently read about using PVC to save on cost. I am considering running all PVC and wanted to know what you guys think before I spend any money buying the 4" saddle taps I had chosen for this main trunk. Is PVC that much cheaper? What are the pros and cons of both? What needs to be done to a PVC system for grounding? Any input, ideas and sources for ducting would be greatly appreciated.


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## dbhost (Jan 28, 2008)

S&D thin wall PVC IS quite a bit cheaper than thick wall schedule 40 PVC, or just about any metal ducting. Depending on where you are, humidity and all, static can be a concern with PVC, some guys ground it, I see no need here in muggy coastal Texas...


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## rrbrown (Feb 15, 2009)

dbhost said:


> S&D thin wall PVC IS quite a bit cheaper than thick wall schedule 40 PVC, or just about any metal ducting. Depending on where you are, humidity and all, static can be a concern with PVC, some guys ground it, I see no need here in muggy coastal Texas...


I agree with db on everything. I would add that the static issue or dust explosion has been discussed and argued so many times which in an industrial setting could be a real problem. However in a home hobby shop you will never have the amount of dust and circumstances needed for it to be a risk.

As db said in Louisiana or Texas there is little concern for grounding to prevent static shock. Now in PA where it may get cold and dry static shock may be a concern but dust explosions still would not be. In all the research I have done and all the arguments about dust explosions, no one has ever provided proof of any dust explosion in a home shop environment. 


I also noticed you said you were considering using all PVC. If your replacing the metal duct with PVC the fittings needed are expensive.

As for the saddle taps I would not use those. As the dust and debris is sucked up the 4" pipe it and the air will slam into the top of the 6" duct there by slowing the air speed down making the system less efficient. A sanitary Tee or a Wye is the best way to do it . Either of those have a curve/angle that directs the air/debris in the direction needed so it don't slow down.

Saddle Tap









Metal Wye










Sanitary Tee










Ken I would do it right the first time because if not it will cost more later. Anything that slows the airflow will make it less efficient. depending on how many things you have in the path they can multiply the problem. 

Another thing that would help make the system work more efficiently is to run the 6" pipe as far as you can. Mine reduces down right at the equipment so the suction is at it's peak. the further you run the 4" pipe the slower the air speed gets.

By having 6" run all the way to the equipment it also allows you to split the 6" duct to smaller sizes for multiple port tools like a Table saw or Band saw without losing the efficiency of the system.

I'm sure you bought a bigger dust collector because you wanted a good efficient system so don't waste that money if at all possible.


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## jgt1942 (Mar 15, 2012)

Take a look at Bill's site (http://billpentz.com/woodworking/cyclone/index.cfm) he has a lot of great info. Go with the PVC, it is much easier to work with. On Bill's site he has an article about making your Wye - you do NOT want sharp 90 degree turns! They really restrict the air flow. Also look around for making your blast gates. A lot of what you can buy have too much leakage. I found a great SketchUp model of one which I will build (see the attachment).


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## jgt1942 (Mar 15, 2012)

Sorry but the attachment did not make it in the above post. I'm trying again.


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