Part of my efforts to reorganize and setup a shop in my barn includes running air compressor piping. My thought was to run a loop around the entire inside exterior walls, which amounts to a little over 200 ft. After doing a little reading it looks like my logical choices for the type of pipe are black steel, copper and the coated aluminum pipe specifically for compressed air. I'm able to do the black steel and copper easily enough but still haven't decided which direction to take. I like the idea of copper for the ease of making changes if necessary. The black steel is of course cheaper but adding future outlets would be difficult. It's also not as clean as copper. The specialty aluminum stuff sounds good but I'm a little concerned about the plastic fittings and cost. Any suggestions or advice would be appreciated.