Originally Posted by Hydro Junkie

And I'll bet you're talking a home air compressor, which is a totally different animal since the second stage does nothing more than increase the pressure capability of the pump when the tank gets full. Never seen a turbine compressor, always recip types with either one or two cylinders, the second being smaller in diameter than the first for the increased pressure output. BTW, I used to work at a shop that sold, maintained and repaired compressors so you're not going to fool me with that one. On an added note, there are also tankless constant run compressors that use a pressure switch to operate the inlet and outlet valves. These are almost always used in industrial settings with a dryer unit between the compressor and the load