Only in my first weeks of WFP and am using anywhere between 50 to 75 ltr per house on first cleans, don't know if you think thats excessive but really want to make sure I do a good job and hope the usage will fall in future.
Aiy caramba!!
I promise you that your usage will plummet once you get the hang of what you are doing.
If we say that a standard semi has 10 to 12 varying sized windows, and is all UPVC then on repeat cleans you should be able to clean those windows with no more than 18 litres at the most, and possibly less than 15 litres with practice.
Those with trolley and back pack systems are understandably more aware of how much water they are using, when you have a 650 litre or 1000 litre tank of water in your van you are very much less concerned.
Now I am a full van mount and operate with the pump flat out I'm probably using 20 plus litres per semi.....
I'll have to point my brush into a bucket and let the water run for ten minutes and see how much I use, as ten minutes is the maximum in actual work time I'd take on a 12 window semi.
I don't bother to turn off the flow between windows either, so I guess I'm wasting water by doing that, not much...but it adds up.
Ian