Peter, New to this group, not sur how to reply to your Blue shaded background message just getting over terrible flu.
Silly, Backpack, its what I have always used, tried putting it on various types of wheels but in domestic situation they just slow me down and get dirty. Dont think that many others have made their own, OTT wont make one cause of health and safety issues.
Mine is an 8 litre container above the smallest Flo Jet powered by a 12v Clulite sealed rechargeable battery like you find in the big handlamps, strapped on an ex army alloy "radio/difficult load" carrier. Its about the same weight as a pair of alloy ladders.
I use a domestic 3 stage RO unit that tap pressure slowly fills into a storage tank, then I tap off into plastic 5 gall contaimers and carry 2 around with me which last about a day. As i am am really careful with my water and switch off between windows if they are far apart.
Peter yes you can get acceptable results with more water, just that rookies expect "everything now" and are impatient if they can find some windows that sheet then at least they dont pack in before they have started ?
Jeff Brimble