Here is something interesting!

The past summer, traveling thru Alentejo province (Portugal) I took a look at ruins of Roman villa at Beja. On my way back I ( it was late evening) spotted 2 Westies parked in the woods. I approached them and witness a guy taking a shower. The real lid was up and the shower head was attached to the lower edge of it. Both campers were from France. That was a disappointment, because most French purely speak English, and  Deutsch. 
I saw once in USA a Westy with a black rubber tank placed in a roof tray. In that case the water in the tank was heated by the sun and used for showering in similar fashion as by French. Their French Westies, had plastic tanks in the roof tray, but the water was heated by a heatexcanger - a small and yet very efficient one made by Laval (Sweden). I asked questions and was shown the set-up. The heat exchanger was familiar to me: I used it in USA - about 30,000 BTU capacity. Located next to rear heater under the rear seat it took very little space. The engine was running and I understood that the coolant was heating the water from the roof tank. In my estimate, except the tank, the system was about $100. 

I wonder if the list ever discussed hot water issue.

Ark.