Originally Posted by
David L Morse
I've seen videos and forum posts on several shops where this has been done. The best setups use a central vac because those have enough pressure to work with long runs of duct as small as 1.5". A shop vac works well with 2.5" PVC. It's pressure loss is only about 6" per 100' at 100 CFM. A typical shop vac has around 80" total available so not much loss for that duct size. Electrical conduit is available in that size and has the advantage of very long sweep elbows.
It can be really useful for things like mitersaws and radial arm saws where you need the high volume of a DC for large area collection as well as high velocity for the small dust ports on the blade shroud. I used that combination for my old table saw. DC to the cabinet and shopvac to the top. I worked very well. I had a run of 30' of 2" up to, across, and down from the ceiling for that.
Note that loss triples for 2" PVC. While still not terrible compared to 80" it can be a noticeable difference depending on hoods and port sizes.