Mike we started out in New England about 20 years ago with a pure water system , we just brushed the windows with an Unger pole with a brush head attached then Pressure washed the windows with pure water it worked great about 50% of the time ,but its a handy tool to have when you vet your work for it
, I believe over here you can rent a di- system from Culligan or other water purifying co,s and the diy unger pole would probably be effective if you were not using it all the time, We gave up on the pure water system about 1996 as it was more trouble than it was worth but i am considering getting a cheapo diy setup for those certain jobs , i picked up a 45ft tucker pole the other day free from a customer who had tried to hace his maintenabnce guys clean the windows, Ive only extende it once to see what it was like and while it was light it certainly felt like it would be hard to work with,
If most of your work is restaurants and the like then Im guessing its probably not worth your while but you would be better served gettin advice from people who use them theres a US forum called WIndow cleaning network or something like that its run by Gary Maur whos the scratched glass specialist
www.scratched-glass.com there should be a link on there for the forum Best of luck Pat
www.window-cleaning.net