jeff & all guys with limited water
why not buy a 10ltr di canister and carry it in car/trailer as this would allow you to make pure water on demand from customers outside taps, just top your tanks/barrels/backpacks up as you go? 
Hi Mac
I won't need to in the new year, I'll have my 250ltr tank with me, I was only using the backpack method to give me a go with my new toys.
I was not use to the amount of water I needed for say one house,so I over estamated, if I had six 25ltr drums, I probably would have took them for one house, I'm a clear case of inexperience.