Of all the things in your pack, water likely weighs the most by volume. Think about it: One gallon weighs about 8.35 pounds. If you’re in the desert, or on a hike where water is scarce, you’ll need to carry enough to drink. But plan your meals carefully, evaluating if it makes more sense to pack foods that don’t require cooking water.
If you’re hiking along a stream or river, you may not need to carry more than a liter of water at a time. When it’s gone, refill your bottle and treat its contents with pathogen killing chlorine dioxide pills or choose a system, like Sawyer’s Squeeze Water Filter ($40) that’s lightweight to filter out the dangers.