[sourdough]

Look underneath closely and see how many lines extend below the belly with a valve on them. There should be 3. If you're looking at a single line coming out you may be looking at the fresh water drain and missing the other 2 which will probably be side by side. Where? Who knows. In the most unexpected, difficult location? Probably. Look behind the frame rails for sure.

When you find them and use them for drains your hot water heater won't usually drain well. I remove my drain plug (Atwood). I believe the Suburbans have an anode rod you need to remove. Also helps flush the sediment, if any, from the bottom of the tank.