how many average size windows would a 25l barrell clean? on the subject of wfp
First cleans you'll use loads of water; since you're inexperienced; and will go overboard wanting to do a good job.
Eventually you'll calm down.
Also, it can depend on different systems and flow rates, but if you're getting a backpack, you should comfortably get the tops of three average semi's done with 25 litres; after you get over the 'first clean syndrome'.
If you want me to be 'anal', that equates to five windows per house, with a 2 litre per minute flow rate, with 1.5 litres spent on each window.
However, I spent an hour with a Freedom Trolley User this evening (don't groan guys), and he uses far more water than I (doing 'tops only') on similar sized jobs; because he can't switch the water off without returning to the trolley, where-as with a backpack and using a pole with an outside hose; it's easy to nip the hose and stop your pump.
I cleaned the tops of one house for him and he's now planning to get a similar set up to my own. Actually, the SAME set up.
Zeus, if you can, try and spend an hour or two with a WFP user prior to using a WFP. Failing that, make sure you practise on various houses first and DON'T be disheartened when your first efforts leave spots everywhere.
There's a knack to it.
After 11 months of using a WFP, I'm 99% percent confident that I leave 95% of windows sparkling, and the other 5% are never noticed or complained about; so who cares.