There are 2 lines on your Fresh water tank. One is the drain line which you stated you have used and the other which should be very close by is the overflow/vent line. The over flowis how you know the tank is full. The low point drains can be anywhere. they will also be together. One newer ones are red and blue. Hot and cold. My '02 5th wheel they are both white. They both will have valves on them. There is no water heater drain hose. You empty the WH from a plug in the tank.
2011 Keystone Sprinter 323BHS
Port Charlotte Fl/Hinsdale Ma
Retired Master Electrician.
I know you believe that you understand what you think I said but I'm sure you realize that what you heard is not what I meant