If you are serious about storing water for an emergency you should make an investment in larger containers. Most containers come in 1-, 5-, 7-, 15-, 30- and 55-gallon sizes. The best choice is the 55-gallon polyethylene (plastic) water drum.
Remember, the average person in an average climate needs at least one gallon of water per day (two quarts for drinking and two quarts for cooking). When you consider that the average person uses 14 gallons in a normal day you realize that cutting back to one gallon per day is truly “roughing it.”
Containers should be stored close to ground level and secured to prevent breakage or possible injury in the event of an earthquake. Containers should be stored away from harmful chemicals or foul-smelling products — especially if stored in plastic which tends to absorb odors. The containers should be elevated a few inches off the ground and rotated annually to ensure freshness.
If you are into recycling, use two-liter pop bottles to store water. Plastic milk jugs are not good containers to use because the plastic will break down over time.
(Source: Emergency Essentials’ Tips For Preparedness)