Plumbing my garage for compressed air...

Mine is done with Copper and it is behind the Drywall. This was all done during construction. Some guys use a water separator right at the compressor outlet into the wall, I dont. I have 8 quick connectors in my shop and I use the bottom of the compressor bleed to get rid of any condensation. I pull the plug and let it out a couple times per year, not a super heavy user of the compressor but it makes jobs easier when I do need it. I use it to blow off the shop floor and it works great.