I would be interested to hear what those of us using vans do about their water storage. Im not yet full time van living but my idea is to use 10 or 20litre plastic jerycans filled as and when i can obtain supplies,be that from taps or streams(I have suitable water filtering equipment)Plus any water for drinking will be boiled first so no problem with bugs!
Waste water will go into separate cans to be emptied at suitable spots.
I want to live as simple as possible which I know does not suit everyone. I dont see a huge demand for water use daily as for personal washing one can do a simple wash down or a shower(in my case it will be one of those solar bag jobs)