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

"trs80" wrote in message
...
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 pipe route.

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
6" route.

Any thoughts appreciated!