There has been a lot posted here on hotrodders about plumbing in air systems, I have about 140 Ft of 1/2 Copper pipe in my shop. when I run a pipe along the wall it slops down to a drain at the end ..I put in a T with the outlet pointing up for the drop. plumbed with a upsidown U so the air goes up over then down with the snap fittings. that way any water will tend to run down the pipe to the drain. There was a tip posted a while back about using an old propane tank with new fittings added , Fill the tank with kitty litter and run the air thru it to absorb any moisture. I have the pieces, just need time to weld it up for the Plasma air supply.