I use a three liter camelback bladder. I have used other brands, and popped them, and some I didnt like the flavor the material gave the water after 24 hrs.
In hot weather, I can go through that 3 liter in half a day hiking, cooler weather, I can make it last all day or day and a half. If you dont drink enough, muscles will start to remind you of it fast enough.
My buddy I go with carries two of them, but then again he is literally built like an ox, so I dont think he pays attention to what it means to have extra weight.
Some guys like em lighter and know they will be near water. I like to be prepared. At least take it in heavy, if your near water, you can always refill it halfway at a time later and still have the extra capacity when needed.