If you can't maintain a downard slope and end up with a "dip" in the line, you might want to add a condensate valve at the low point to let the water out. Best to have some way to access it for service as they plug up at some point. Not selling McMaster Carr stuff, but an example is their part number 41645K47. Or a pin hole would work with minor loss of air. Condensate freezing issues are a difficult problem in cold climates. I calculate you would need 10 gauge copper to run 230 volt single phase 1/2HP over 1,000 feet, with loss of ~10 volts, if that helps at all. Best of luck!
