I just bought this craftsman 6hp,33 gal. air compressor used from craigslist, it work's great but it's my first air compressor and I would like to find an owners manual so I know all of the maintenance procedures to follow. I was trying to drain the tank when I first got it, very little residual water was on my fingers. Should the valve be letting air out as well and or should'nt there have been more water.