I've had a 3 gallon pancake style tank sitting in my garage for about a year or so now after purchasing my SilentAire 20A. The tank was from a Harbor Freight 3 gallon 100psi oil-less compressor. The original configuration of the compressor was VERY loud and refilled constantly during use with only a 15psi differential between the cut-in and cut-out pressure.

The donor compressor didn't have much to offer for parts other than the main tank, power cord, safety valve, and gauges. I had to cut off the 2 risers for the original handle and plug the 2 smaller 1/8" bungs on the top of the tank for the original air input and pressure switch as I would not be using those.