# Main Trunk sizing



## Dougj2 (Feb 20, 2021)

My shop is about 15ft x 20 ft in size. I purchased a King 1200 CFM dust collection system that comes with 2 outlets that have a 3 7/8 inch OD. I have some non static flexible 4" pipe to run to the various machines (6 in total) but need to run a main trunk line the length of the shop, from which I will drop off the feeds(using the flexible pipe mentioned earlier) to the various power tools. 

I bought some 4 inch PVC pipe to use for that main trunk line but its OD is 4 inches so the flexible pipe will not connect to the 4" OD PVC. I also read that perhaps I should be running a 6 inch trunk line. What is my best size trunk line to run and what exact type of pipe should I be using for this main trunk line. As well I guess I would nee adapters to run from the main trunk to the machine feeds so my question is, in Canada, where to buy these parts?

Thanks for any help.
D.


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## John Smith_inFL (Jul 4, 2018)

Doug - welcome to the forum.
if you are using the 4" thin wall (sewer) PVC pipe, you can enlarge the end to a bell fit by heating it gently with bottle torches, weed burner, kitchen stove, electric hotplate, heat gun, or whatever you have and are comfortable with.
practicing on scrap pieces is always a good idea. and have something available to form the end once you get it heated. (the same heating process can be used to reduce the end size down if needed).
in my area, 4" sewer pipe is 4" OD with a factory made "bell" on one end for connecting long runs.
have you considered this ?


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## Dougj2 (Feb 20, 2021)

John Smith_inFL said:


> Doug - welcome to the forum.
> if you are using the 4" thin wall (sewer) PVC pipe, you can enlarge the end to a bell fit by heating it gently with bottle torches, weed burner, kitchen stove, electric hotplate, heat gun, or whatever you have and are comfortable with.
> practicing on scrap pieces is always a good idea. and have something available to form the end once you get it heated. (the same heating process can be used to reduce the end size down if needed).
> in my area, 4" sewer pipe is 4" OD with a factory made "bell" on one end for connecting long runs.
> have you considered this ?


Thanks John. I can give that a try.

Doug


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## woodnthings (Jan 24, 2009)

Dougj2 said:


> My shop is about 15ft x 20 ft in size. I purchased a King 1200 CFM dust collection system that comes with 2 outlets that have a 3 7/8 inch OD. I have some non static flexible 4" pipe to run to the various machines (6 in total) but need to run a main trunk line the length of the shop, from which I will drop off the feeds(using the flexible pipe mentioned earlier) to the various power tools.
> 
> I bought some 4 inch PVC pipe to use for that main trunk line but its OD is 4 inches so the flexible pipe will not connect to the 4" OD PVC. *I also read that perhaps I should be running a 6 inch trunk line*. What is my best size trunk line to run and what exact type of pipe should I be using for this main trunk line. As well I guess I would nee adapters to run from the main trunk to the machine feeds so my question is, in Canada, where to buy these parts?
> 
> ...


It's "common" knowledge in dusty circles, that the larger diameter the trunk is, the better the performance in collecting fine dust, no offence meant! Also ribbed hose affects performance as well, so that's best kept to minimum lengths. The "go to" source for dust collection online is Bill Pentz's site here:


Bill's Cyclone Dust Collection Research - Home Page


Look under "ducting" then "pipe size":




__





Dust Collection Research - Ducting


This site helps small shop workers understand the risks from fine dust exposure and how to effectively protect themselves and their families from airborne dust hazards. Fine dust is so extensively studied that researchers call it PM short for particle material. A Google search on PM Health Risks...



billpentz.com





Not everyone will be as "obsessed" as he is but he has health issues that require it. I've been reading the pages for years, but still feel I don't quite get the complete picture, just enought for a basic understanding. Air flow is a lot like electricity, you can't watch it move inside the pipes, you just know when it's not working and there's dust everywhere. Give it a read, and you'll know and understand much better some of the issues!
Can't help with sources and prices in Canada, but we have a few members there who can.


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## B Coll (Nov 2, 2019)

Dougj2 said:


> My shop is about 15ft x 20 ft in size. I purchased a King 1200 CFM dust collection system that comes with 2 outlets that have a 3 7/8 inch OD. I have some non static flexible 4" pipe to run to the various machines (6 in total) but need to run a main trunk line the length of the shop, from which I will drop off the feeds(using the flexible pipe mentioned earlier) to the various power tools.
> 
> I bought some 4 inch PVC pipe to use for that main trunk line but its OD is 4 inches so the flexible pipe will not connect to the 4" OD PVC. I also read that perhaps I should be running a 6 inch trunk line. What is my best size trunk line to run and what exact type of pipe should I be using for this main trunk line. As well I guess I would nee adapters to run from the main trunk to the machine feeds so my question is, in Canada, where to buy these parts?
> 
> ...


My shop is not, and has never been dust free. Never will be. My dust collection system is all 4", with drops and blast gates at every machine. That said, some machines produce less (visible) dust than others. My planer produces almost nothing. My table saw still produces plenty of dust coming off the back of the blade. Spindle shaper still produces some dust. Then, my hand power tools produce plenty of dust, even hooked up to the system. My hand planes make dust as well as my chisels, spokeshaves, and rasps. Some may measure microns in their shop. For me, the dust collector is a tool that assists me in keeping my workplace relatively healthy and clean. I have worked in plenty of shops, have not seen one yet without sawdust.


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## ducbsa (Jul 6, 2014)

Pneumatic Transport and Conveying - Carrying Velocities

Duct Velocity


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