Manual water tank heater hose: see update in first post

westend, I see what you are saying -- use the drain opening. That's a possibility. I think, though, that the "right" solution would be with internal plumbing -- and if I lived in the Northern US and wanted to do a lot of sub-freezing camping, that would be the way to go.

For those of us who rarely encounter freezing conditions, my half-baked method might be just adequate, even if it is Mickey Mouse style. ;)