I'm an old-school builder- - - -air lines will be black iron pipe, probably 3/4" NPT. I've seen a few shops plumbed for air with PVC, but I've also seen the aftermath of a couple of pipe fatigue fractures using that stuff. The main thing to remember is just like with any other plumbing, "Schtuff" flows downhill! Air lines need to have enough downward slope to allow a drain at the end of each pipe run to effectively eliminate moisture, and the drains should be opened frequently! I'll probably incorporate a refrigeration-style drier somewhere in the system, but NOT close to the compressor. Hot compressed air is very difficult to de-water. I like to run the air compressor output pipe up to ceiling level, all the way across the shop, then plumb it back down to floor level to the drier. That puts distance and gravity on my side so the drier has the best chance to do its job effectively.
Jerry
