Welcome to the AD world. We think it was Horizon's best floor plan. You can drain the water heater by opening the pressure release valve AND opening the drain plug. Pressure release valve is towards the top, and the drain plug is towards the bottom of the water heater. If you are storing for winter, you should drain the WH to keep the water from going sour.
If you are storing, you should retract the jacks. Some people don't like to store tires on concrete. They prefer to park on boards placed on the concrete. Theory is that water will become trapped between tires and concrete. That water can deteriorate the rubber. My opinion: not an issue because you aren't keeping it in storage for a long time. You should cover the tires, though. UV damage happens 365 days/year.
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if you have any 40AD questions.