I have a backpack on a very light shopping trolley frame. Wheel it where I can, and carry it where I can't. Dai
Dai,
For the past few months I've been pulling 25 litres of water behind me and just carrying the backpack, either in my hand, on one shoulder or both shoulders, and just topping up from the 25 litres when required.
I rarely carry the backpack more than half-full, because it's heavy and I don't want to get any manual handling injuries; the wimp I am.
I'm quite happy to top up at every decent sized house I clean with it, it takes seconds to top up, but usually I can clean two semis with a half full backpack.
For larger properties, where I WFP everything, I will fill the backpack to the top and put it on the trolley.
I think the beauty of the backpack is that it gives you complete freedom to really go anywhere. It gives you far more freedom than the Freedom Trolley!
You've just got to work out the best way to use it for any given situation.