DIY air separator

[Toolmaker51]

Very nice. And copper is not only safe for compressed air, it should conduct heat away from air better than black or galvanized pipe.
I'd add two things. A small separator at inlet; plexi bowl would make accumulation visible. Using petcocks or needle valve drains instead rather than ball valves, being easier to 'crack' open.
But it works! Not only Portable but Attached; big step saver.