Van Build - Water System
We adopted a simple approach.
Storage
We use 3 water tanks - 1 for grey water, and 2 for clean water. They are secured to the floor, using bungees.
Pump
We installed a 12v water pump. It is qutie easy to install, and runs quietly.
Connecting pipes
The most time consuming part is finding all the fittings/adapters. We spent several visits to HomeDepot and returned multiple online orders. It is confusing.
I am not sure how much our lessons can be applied to others, because all the sizes might be different. One advice is to bring all the stuff you need to hook up and spend a few hours in the hardward shop and fit everything.