I have a theory that it takes a certain amount of water to clean a window, it probably takes the same amount of water if you have a lower flow and spend more time doing it.
Lets say your set at 1 ltr per minute and you spend 1 minute doing a window then you have spent 1 ltr. If you go to 2 ltr per minute you should be able to do the same window in 30 seconds, also 1 ltr a minute.
Obviously you need to agitate a little quicker but if your aware that your water may go down quicker then that itself will speed you up, you basically have to work according to the speed of your flow. I f you come across a window or even house that is going to take you longer for whatever reason, effectively slowing you down then it would be wise to turn the flow down too.
I find the key is to evaluate your windows before cleaning them, if there is something like bird muck there then wet and scrape it first If your working on a house with all sheeting windows and they're free of anything problematic (most maintenance cleans) then you can fly through them.
I never used to properly look at each window before cleaning it, I was trying to go quickly so I would just bounce from window to the next without looking and just give it a real good scrub in-case there was something I hadn't seen. Was hard work! Now I have slowed down and taken the time to check it has speeded me up (if you get me) a lot and is much less hard work.
I carry a scourer (white top) and a 4" scraper in my pocket for bird muck etc for downs and have super scraper and scraper attachment for the ups, scrubbing with the brush is very time consuming and takes a lot of energy. the less the best.
