Sorry CharlesOK, I was misremembering from last year when I first looked into this issue - I saw lots of valves under the tight-space-under-cabinet and was totally confused.
I do remember seeing a pull ring under the cabinet close by the WH (and one under the dinette by the FW) which I think are the water line drains. I guess the pull ring drain near the water heater cannot drain the WH, only local water pipes, right?
As I recall, I was put off of ever unscrewing the WH plug outside the RV because I thought all 6 gallons would end up on the RV floor and hit the electrical stuff nearby. Does the WH drain go out into the air and miss any RV hardware?