Coiled under the bed? Think filling and the overflow tube. You really don't want water under the bed with the heater inverter, etc. That are also under the bed.
I guess another thought is... Do you avoid rain? Do you wax the paint? I personally can't see anyway of avoiding getting water on the outside from pretty much any source unless you want to park it in a sealed garage and never take it out.
I am not trying to be a smart a$$, I just figure getting the outside of the RV wet is part of using it.
My bad, I wasn't very clear.
I would replace the current overflow tube with a longer, say 3' piece that would still connect to the outside. That's what would be coiled under the bed. No water under the bed.
I only look stupid...
Plus, all water is not created equal. Rain spots wash off easily, it is soft water. The hardness and types of minerals in your water supply determines how difficult it is to remove those spots. And yes, a good polymer paint protector like Dry-Wash helps make it easier.