As per the survival rule of threes, you've got about 3 days before you are incapacitated due to lack of water. That puts it among your higher survival priorities in the grand scheme of things.
Water weights about 8 lbs. a gallon. The US Army recommends a daily consumption of 50-75% of your body weight in ounces, depending on your level of activity. 1 gallon = 128 ounces = 4 quarts. So, if you weigh 150 lbs.: 150x.75=112.5 ounces or .8 gallons That's about 6 1/2 pounds for each day's worth of water.
Now let's think 72 hours, because a lot of preppers like that time frame for short-term emergencies. 72/24=3 days. 3x6.5=19.5 lbs for your water supply for that period.
Due to the weight and bulk of water supplies over a period of time, a lot of us get water filters to help provide for our hydration needs.
My primary field filter is an MSR Waterworks. I picked this one because I liked the construction quality, maintenance parts were readily available, and you can clean the filter (and restore full operation) with a steel wool pad. The Waterworks is discontinued, but you can get the MSR Miniworks, shown below:
That would be my primary filter. For a secondary filter system, I found these Frontier Straw-type filters:
I picked up a couple back East, but haven't been able to source them locally. I did, however, find a better substitute made by Sawyer:
It comes with a small 16 oz water bag, but can be attached directly to plastic soda/water bottles you may scrounge up along the way. You can also use it as a regular straw filter.
Throw one of these in your kit, and at least you won't go thirsty.
I don't care for Camelback-type hydration bladders after I had one spring a leak in a pack during a hike. I stick to 1 and 2 quart GI Canteens, and Nalgene bottles. The GI canteens have a cup and stove that fit over them in the canteen pouch, and the Nalgene bottles screw directly onto the bottom of my MSR Filter. The MSR will also screw onto the bottom of a Camelback for those of you who run them.