[franken]

I have 3/4" black pipe but built it so water has to drain back into the tank, or blow through the outlet end via traps and filters. No place place for water to collect makes for little rust. It also makes it easy to purge water.
The systems w/ vertical long runs and short horizontal and many valves make no sense to me. I might be full of crap, no doubt. I'm also speaking of a 2 car garage in suburbia, not a big shop. That said, I have a light commercial grade (Saylor-Beall) 80 gal compressor.
I drain water from the tank by purging (not draining) when I think about it so generally I start w/ cool air.

Let's not get started on the PVC suicide pipe. That's nuts. Leave a piece of PVC outside for a few months, then drop it on the ground. Shattered.