Thanks to all who replied. You gave me enough clues to navigate around the 2250S. 2012 is the first year for this model, so FR did a lot of engineering/re-engineering on the fly. Removing all panels did not show me anything but the tank, pump, and Hotwater heater. HOWEVER, for other 2250 owners, removing the drawer above the heater vent next to the bed allows you to snake a hand behind the H2O tank and feel the valve. Blindly opening/closing it does the trick!