Coachmen likes to put all sorts of water system valves on a central control panel. Mine (a much Coachmen Santara) has five on such a panel that are somewhat opaquely named, but actually end up being the water tank fill (from the pressure side of the system), winterization (or pump fill) suction line shutoff, hot and cold low point drains, and (I believe) a shutoff for suction from the tank to the pump. Nearby (but not on the panel itself) is the fresh water tank drain valve, the equivalent of what you're looking for.
The brochure for the Leprechaun 280DS only suggests that the drain valve is near the tank somewhere...not the most helpful. I guess probably that implies it's not on the fancy control panel.
Despite the initial confusion and complexity, it's actually a fairly convenient system to use once one figures it out. The only "hidden" valves of interest are the water heater bypass valves for winterization, which in my case are located underneath the kitchen cabinetry and accessed by removing a drawer. Invariably they would be close to the water heater, wherever that is on your unit.