Hi,can anyone tell me if these are actually any good? Im basically just looking for something to use for the odd hard to reach window and dont know if its necessary to get a trolley. How is the water purified on the backpacks? Also will a window cleaning pole fit on it? Do you always need a outside tap? Can they connect to a 25L barrell? For the sake of maybe 5 houses a month which have difficult windows it seems like a good idea but not sure how good they actually clean the window? Any advice please guys.