Would a small shop DC system run ok with the mains at 4" smooth bore PVC
ducting vs 6"? I would have about 30' of main and 4 drops using a 2hp
1600cfm unit and air blocks for the station no used. The DC has a 5" intake
and 12" impeller.
I cannot find locally PVC 6" sewer and drain pipe. I can find galvanized 6"
duct at about $1.40/ft and 4" smooth bore S&D PVC pipe at $0.58/ft. I hate
to spend more of the duct then the DC which would happen if I go the metal
I visited all local Home supply brands (HD, Lowes, CW) and all dont carry
over 4" pVC. And I called an irrigation supply and they dont carry the
light duty 6" PVC pipe (i think its schedule 2379 or something like that).
Im guessing that its not a big seller inmy area for some reason to do with
building codes for such things.
So any way, I was wondering how much performance I lose by going the 4" vs
Any thoughts appreciated!
In sheer volume of air moving, quite a bit of "performance loss". But
with this much suction, I don't think you could improve the dust
collection any better than "all of it", which you'll probably attain
with this set-up. I think 4" is plenty for now, 'til you add on to the
For 30' of straight pipe, one wye, and 6' of flex hose, the 6" gives
2.25 inches of pressure, while the 4" gives 3.57 inches.
Whether the additional pressure is a problem will depend on the fan
curve of your blower, hood losses, separator losses, filter losses, etc.
You could check with Penn State Industries for metal ducting and they also
have a design service. Also, remember that the more unusual the size or
material the harder it is to get wye's, elbows and connectors. Even with
using the 4" PVC I had to do a little fanigaling to make connections but at
least it's doable. Your runs sound like mine and I'm having no problems
with my cheap Harbor Freight DC and a 4" PVC main. I use gates right where
the wye splits from the main for more efficiency (there's a name for that
run from the wye to the gate to the machine and I decided to eliminate it).
I also ran my main trunk at the level of the DC inlet so that the machine
cuttings drop down to it further eliminating an element of resistance. Of
course, anything I gained there I lost with the corrugated flex line from
the machine to the gate at the wye. It's a bit of a balancing act and I let
myself get tangled in all the technicalities for a couple of months before I
just went ahead and 'made do' with the 4" main. I wasted a lot of time with
all that fretting. Just do something. Oh, one more suggestion. Don't
fasten everything with pvc cement or even caulk. Just drill and use
sheetmetal screws until you're sure that you're satisfied and even then I'm
sticking with this set up. It's easy to access in case of any issue such as
a clog (got leaves stuck in the metal 'X' which protects the impellar.
What did you do for the blast gates? I assume something that senses what
machine is on and then opens the gate?. Those look like they can get
expensive. And to make something manual would not allow the gate to be near
the main as it would be awkward to reach each time and odds are I would just
leave it on.
I am currently using the setup your suggesting, only with a slightly tricked
out Jet 1100cfm DC. Two zones 30ft or so 4" SD pipe w/4 drops on each zone.
I don't know how much better 6" pipe would be but I do know it wasn't
availiable locally so I used 4" and it is working fine for me. The first
zone runs from separator up to ceiling across to right side of TS and back
down and catches planer, TS, overhead guard and jointer. The second zone
runs from the separator along one wall and catches the router table, band
saw, one fitting for a future sander, and it finally reduces to 2 1/2" to
facilitate shop vac hose/fittings for cleaning the shop. I put blast gates
at all the machines plus a blast gate at the start of each zone so the DC
isn't trying to suck air from the zone not being used. Someday I'm gonna
pick up an anemometer just for kicks... Anyway, I'd suggest just using duct
tape to join the fittings and pipe together. If you decide to change the
configuration someday, it's easy to just cut the tape and pull it all apart.
Also, avoid 90 deg elbows wherever possible, they will tend to clog. I
switched to 45deg fittings to make smooth corners and haven't had a clog
since. I found some reducers in the schedule 40 area that fit the 4"SD and
reduced it to 3"pvc (IIRC) that the flex pipe fit over perfectly. I'll
second looking over Bill Pentz website, information overload on DC's. --dave
I tried 14 different wholesalers for pipe in my area. Not one carries the
6" PVC S&D 2379 (thin wall inexpensive pipe). SOme said they could order
it. Most had 6" SDR-35 which is about $2.50/ft.
So my options are down to using the metal ventilation 6" pipe ($1.40ft at
Lowes) but I hear the adapters are very expensive....or.......
Keep all ducting at 4" PVC thin walled ($0.58 at Lowes).
Just a thought here, and I'm not throwing stones.
After visiting that many locations, how much time & money did you spend
in the travel?
Yes, there is a difference in what you use, and how efficient it is in
getting the last iota of dust and debris from the output of your
machines. But after a while, there is diminishing return from the
quest. You're still going to hand sand, cut with a hand saw, chisel or
hand plane. Dragging in stock, particularly rough or log style, brings
in crud. At some point, there is going to be extra stuff on the floor,
on your clothes, and in the air.
Your grandfather worked that way. So did my uncles. The last uncle
died with a grin on his face at 94 years old last spring.
So decide. 4", or the 6" you can get. It's only money.
I put in the 4", if that means anything to you.
uhhhh....it was phone calls.....not driving. Took 40 minutes. Its
someting we enjoy here in California, modern communications. I hear it will
be spreading to other parts of the country in the near future..
I had to laugh! I live near SF, have been in the telecomm business for
most of the last 25 years, and would likely still have gone and dug around
the yard. Yeah, right.
Have fun with you new stuff!
Well, 6" is better than 4", and 4" is better than 2". The larger pipe
simply can move more air. There are other factors like length of
pipe, turns, turbulence, etc. Four-inch DC pipe and connectors are
easily obtained, plus many machines are fitted with 4" ports. You can
compensate (a little) with a DC that moves more cfm.
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