I've never carried more than 3 liters at any one time. The places I've backpacked, water was never an issue. If Fresno Creek and some of the springs along the way are all dry when I go do my OML trip in a few weeks, I'll need to pack at least 2, if not 3 gallons of water. I have a 2L bladder and 2 nalgene style water bottles, each 1000ml. I don't want a ton of separate water bottles, and I don't think milk jugs are the most efficient use of space, so I was just wondering what you guys use to carry your water, when carrying 2+ gallons.