when i abuilt my garage a few years ago i used the heavy wall copper tubing for the air lines , its more money than regualr copper but twice as thick . i just used 1/2 for the lines as its inside diam is more than enough to move a lot of air for most equipment.
its also realy easy to solder together as it holds it heat a lot longer.
the body shops i deal with all have copper with water drains