Welcome to the forum, David.
We have a 2005 Monterey, so our set up is the same. As you know, the fresh water tank is in the bay with the Hydro Hot, just behind the curb-side tire. That is where the drain is, of course, and the water drains straight down out of there. My switch to open and close that valve is electric and can be a little cantankerous at times. When I push it once to open it, I listen for the barely audible little click. And then I run around and look under the coach on the other side, to see if water is coming out. Sometimes I have to go push it again. Make sure your low point drains are closed.
Good luck.