W.C. Fields famously said, "I never drink water because of the disgusting things fish do in it." Of course, his liver was the size of his thorax and a vibrant shade of blue, but you have to admire the man's commitment.
For us less-committed but probably healthier people, getting a bunch of water down our pieholes when we're engaged in high-perspiration activities is a priority. Kelty is here to help: their Aqua Porter is a portable canteen that fills the niche between Camelbaks and Lister bags. The 8.5L Nalgene is handy for car and basecamp, but it's packable too if you're going somewhere a filter won't work. A little metric reminder: 1L of water weighs 1Kg or 2.2lb, so you're looking at 8.5*2.2=18.7lb plus one for the carrier, about 20lb packed.
The carrier is solidly built a la all Kelty gear, and the twist faucet never leaked on us. The handles are beefy and there are d-rings for a (not included) shoulder strap. The zipper slash pocket has a cord that can go through a roll of paper towels if you want to set it up as a wash station. All in all it's a great size for weekend warriors or a day at the crags in the hot season. The alternative is one of those monster square things, which are cheaper but a lot more difficult to move around.