This from
http://www.equipped.org/watrfood.htm#SweetWatera site providing information on survival methods and equipment. It states that prepackaged water is Coast Guard approved for a 5 year storage life and tap water is good for six months or a year.
------------------------------------------------------------------------------
"Water and Food Group
I cannot possibly over emphasize THE CRITICAL IMPORTANCE OF CARRYING ADEQUATE SUPPLIES OF WATER. It may weigh a lot (2.08 lbs/quart plus container), but nothing is more vital for your body. Generally speaking, you can survive for weeks without food, but only days, or less in some circumstances, without water. Water is essential for your body and mind to function properly. You need both working as well as possible. The adverse effects of dehydration on your mental faculties, even mild dehydration, as little as 5% to 10%, are insidious and extremely dangerous in a survival situation.
The more arid the region you live in, travel through or fly over, the more water you should carry. The only reliable source of water in the desert, particularly in the summer months, is what you bring along! During the summer months in my desert area I carry a minimum of an extra gallon of water per person. Two extra gallons wouldn't be unreasonable. Minimum recommended for most climates is one quart per person and you should carry more, if possible. Always carry some water with you. In an emergency, for immediate medical or other uses, you may not have time to procure it, even in areas where it is readily available.
Packaged waterYou can use prepackaged water in 125 ml flexible pouches, "flex-paks," (4.227 fl. oz./ 1/8 qt.) (S.O.S. Food Labs and Mainstay are two of the most commonly available brands, but there are dozens worldwide that package this way), 250 ml "Aqua Blox" aseptic packages identical in concept to the boxes juice and other drinks are packaged in, including a little straw attached to each box, (8.45 fl. oz. / 1/4 qt.) or bottled water off the grocery store shelf in plastic bottles.
One disadvantage to the flex-paks and the Aqua Blox, is they have a tendency to leak when squeezed or crushed, as might occur when tightly packed in a survival kit. This is particularly a problem with the flex-paks. Best to vacuum pack them or place them inside a Zip-Lock style plastic bag. The flex-paks are also very easily punctured, so be careful how you pack and handle them. Finally, once opened, the flex-paks must be consumed or the water stored in another container because they cannot be resealed. One option is to pack the flex-packs inside a large mouth water bottle for protection, which also gives you a suitable water container with little wasted space.
TAqua Bloxhe Aqua Blox have sturdier packaging than even the conventional aseptic boxed liquids and thus stand up to abuse far better than the flex-packs. Their boxed shape makes them much easier to pack in most kits. The included straw makes is far less likely that any precious water will be wasted. While they cannot technically be resealed, we have found that a piece of duct tape does a fair improvised job of resealing the package. For most uses, we prefer the Aqua Blox to the flex-paks, but they do generally cost a bit more.
Both the flex-paks and Aqua Blox are USCG Approved with five year shelf lives.
Alternatively, you can use canteens or similar containers. These can be filled at home.
Tap water or purified "bottled" water is generally good for six months to a year's storage if kept away from the light. Or, you can sterilize the water and storage containers like done for home canning, assuming they will hold a vacuum, and it will last for years, just as the prepackaged water will.
An easier way to sanitize the containers is to use an Iodophor solution. Iodophor solutions are iodine based sanitizers commonly used in the food and beverage industry and a typical 4 oz. bottle will be more than enough and it is inexpensive. Almost any supplier of home brewing equipment and supplies will have it in stock and will be able to offer tips on proper dilution of the concentrate and contact time, which generally only takes a few minutes.