I got a van system 175 ltr, soft water area. 2 x DI vessels, with hose.
I started with just a backpack on a trolley but felt that it wasn't throwing enough water out!
I'd have it on setting 3 / sometimes 4 and just didn't get on with it.
I now have 100psi , with eco-flow at about 5oclock setting.
STILL have problems with getting corners clean on really salty /dirty windows (coastal area) they look clean but when you get up close the corners are still dirty! You can wipe the dirt away with your finger / cloth.
I do rinse rinse and proper scrub, x 2 then rinse some more, but some are still dirty!
I fill up at customers houses too. sometimes I fill the whole bottom of the car , when I forget. but then I just park on steep hills!