In looking up the Rockwood 1640esp pop-up, I see that the water heater/outside shower was an option. Easiest (which is not going to be easy) would be to get the package from your dealer or direct from Rockwell. And take some measurements on where the factory option is installed (I assume under the pull-out gaucho).
Does your pop-up already have a water tank, inside sink, and water pump? If not, you will need those items as well.
The normal water heater is a propane-only 6 gal tank. The air intake and exhaust is located on the left side wall of the camper and is attached directly to the water heater. Combustion and exhaust air must be completely isolated from the inside of the camper. The water heater needs a propane line and 12V electric, with a small operator's panel on the front of the seat of the gaucho. Plumbing means bringing a supply line from after the water pump and filter, installing a bypass for winterization, and hot water lines to the sink and outside shower. You must also install a hot water low point drain next to the cold water low point drain.
To be honest, the stereo and the water heater are the 2 least used appliances in our A-frames and previous pop-up.
In the summer, I don't want another heat source inside the camper - some heat is going to leak through the insulation of the water heater.
We don't wash dishes inside, and so rarely use the sink, and don't need hot water when we do.
In cooler weather, I will sometimes turn on the water heater, and use the outside shower as my source of hot water for dish washing and cooking and other cleaning.
Other times - if we have electric hookups - a small coffee pot sitting on the outside prep table plugged into the outside outlet suffices for all the hot water I need. Without electric hookups, a teakettle on the camp stove at the picnic table does the trick.
hope this helps, enjoy your camper
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