Neville

I carry two platypus 1L bottles on the outside and one or more 4L platypus 'water tanks' inside. I plan on one gallon per day and usually limit my trips to three days unless I can resupply somewhere. I wrap each of those water tanks in a garbage bag in case they spring a leak.

Edit to add: MSR dromlites work pretty good and are a bit more flexible than the platypus bottles but my water always developed a taste. No taste problems with the platypus.