Why hasn't a smart RV builder installed some sort of rain catchment system on the roof? I've seen rain collected off an awning. But a tray the size of a solar panel with a lip and an outlet that connects to the tank may be a good idea.
Awnings are basically kept clean of dirt and more importantly bird droppings - any water container on roof would only collect water in an unhygienic container.
I have tank water on my property in bush, gutter guards keep most crap out, I add chrorine to tank - all drinking water is filtered prior to use.
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Possum; AKA:- Ali El-Aziz Mohamed Gundawiathan
Sent from my imperial66 typewriter using carrier pigeon, message sticks and smoke signals.