you need to test the water from your tap with a TDS meter if its low say 50/60 then run the water thru 1/2 di vessels and this will give you the pure water
if it is higher say 120 then run thru a RO filter system first then the di vessel
run the water into a ibc in your garage then pump into a tank in the van ,by running the water into a ibc you will have a stock of water and no need to wait while the ro fills the van
then you just need a pump attched to the van tank,hose reel,pole etc