Water is so important to a safe and comfortable hike that I always carry a water system with backup plans incorporated in it. Starting with a bandana, filter straw, plastic baggies for water collection and treatment, a tiny vial of SweetWater, and some Micropur tablets that are in my tummy pack. I think of that as a survival kit on its own because the round survival tin can be used to boil water. The tummy pack has the minimum needed in a pinch if I were separated from my pack.
In my backpack I have a Katadyn Hiker Pro, more baggies for water collection and treatment, collapsible Platypus bottles for extra water storage in camp, a slightly larger bottle of SweetWater, and more Micropur tablets. On a multi-day hike I take a collapsible nylon water bucket.
That's 1.5 pounds for my water treatment system, at the most, with 3.5 pounds for the shelter system that includes the sleep system. I don't begrudge 5 pounds of health and safety items because my base pack weight is less than 7 lbs before water and food.
Water discipline is extremely important and goes hand-in-hand with sanitation needs. Did you know that you should keep your water intake parts completely separate from your water output and storage items? One drop of unfiltered water is enough to contaminate everything. Water discipline for me starts when setting up camp. I haul in 2-3 gallons of raw water to camp in the collapsible bucket, then filter/treat it and refill my Platypus and fill a collapsible bottle or two for cooking and sanitation.
I never wash up out of the hauling bucket. I wash up using a clean bandana with 8 ounces of filtered water poured from one of the collapsible bottles plus a little Dr. B's, to avoid getting micro-organisms from untreated in my eyes and nose. A few drops of the SweetWater in the bucket makes it a good place to soak the bandanas to clean them up for the next day. After dinner I wring them out and hang them up to dry. I have gotten the curse of the trail once during my early days and vowed "never again". I believe that water discipline helps out with overall health and sanitation needs.