Another operator here (chaz), used an existing vacuum that was mounted near a wall on his building. He piped air to the vac, hung a hose there, and put a switch on the vac to toggle between air and vac. This used the existing vac controls, etc. instead of building/buying a whole new machine, plus getting vacuum price for air. I had the perfect spot for this setup, with a vac on the end wall of my building, but sold my washes before I got around to doing it. Who am I kidding? I was never going to do it.