Is there a proper way to drain the water seperator on a fass 150? Whenever I open the valve on the bottom of the canister it seems like fuel just keeps coming out.

Normal its siphoning from the fuel tank. All you need to do is drain enough to get the water out. few ounces...

Thats a good thing. If you have any amount of water I personally would be filling at a better fuel station.No water is the ideal situation.

Yep I hardly ever get any water out. Maybe just an once or two at the most.