if you are seeking a way to filter large amounts of water
in a back county--long term situation i would suggest a gravity
filter system made for base campers..its a bag that hangs
in some way..a tree?..with a hose out the bottom with a filter
element in it..you fill the bag and without having to pump
or fool around with it it slowly filters your water..so at
nite your making water for the next day..as it's just a plastic
bag and hose with a filter you could have several going at the
same time..a clever person could get a filter and make their
own...i have seen these hanging in camps but never used one
myself..