"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!


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.