Thank you very much fellows, much appreciate this.
Wondering if valves are universal across RVs- whether 90 degree to the line is considered as closed. I think that what 12 man says is a bit different to what Barney says in that regard, but the gist is the same - when I dewinterized I let the pink fluid into the water heater and cant seem to flush it out.
Right now I am on my driveway and worry that will overflow grey water tank but heading out tomorrow to campground and will try again there. Thanks for the tip guys - will also buy a 16mm? socket to remove heating rod to better flush out the tank.