At the risk of sounding redundant, I've discovered that buying 2.5 gallon jugs of spring water at the grocery store is the most economical way of storing water.

Each 2.5 gallon jug costs me $2.50, comes complete in its own container with spout, and is efficient in use of storage space. According to the CDC, bottled water has an indefinite shelf life when stored unopened and out of sunlight. Since we use these for most of our drinking water, I go through one or two jugs a week and rotate through my supply at least once a year.

I would not trust the water dispensed by vending machines to be any safer to drink than my tap water. Who regulates, tests and maintain these machines to determine what level of filtration they provide? You also need to factor in the cost of the container, which will easily put you over the $5/5gal price point.