The thing that popped out at me was your statement that you were packing your 'dry food' so that if a leak did occur, your food would be fine. BUT...what about everyone else's stuff??? What happens if your water leaks and someone else's bag gets soaked??? Sure, your PopTarts are fine, but what about my clothing??
Can you pack water? Sure you can. But it has to be well insulated, and triple bagged. It is a lot of space taken up in the bag. But, if that's your choice, fine. Just be sure that your bag contents are not going to negatively impact someone else's bags!!!! Many here have reported having to replace clothing that was ruined by leakage from someone else's bags.