Originally Posted by
acantor
1. It's easy to underestimate how much water you might need while touring. If you are planning on carrying one bottle, double that!
In the context of touring involving camping and not relying on resupply stops every day - it is attractive to plan resources to measured quantities. That goes for planned meals, etc. A really good idea is to have an extra 2 days of food at any given time. On top of that - an extra gallon (128oz, or 4x 32oz Nalgene bottles) of water than what you measure or anticipate you'll need is a good thing.
The reason being - if you end up stuck for a couple days you can get through. Or, if a planned resupply stop doesn't pan out (if you hit Amish country at 6:00pm on a sunday - you won't find anywhere open) you have supplies.
Another tidbit is having a way to filter water. This can be a substitute for the extra gallon, depending on where you are. If you are somewhere where you aren't ever too far away from a water source (running water like a stream is usually better than lake water, but proper filtering can make either "safe") you can have all the water you can use. Though, in a lot of places streams have a lot of pollution so city or well water is a better bet - so long as you have it or can get it. Hence having extra, regardless of the "weight".
If I run low on water I will filter water for camp duty - scrubbing dishes, washing hands, etc. If I am out I'll use it for cooking and drinking and store up to a gallon, unless I know for sure I'm resupplying the next time I move (IE - have routed to a place to resupply right off the bat).