Plan on having at least 1 gallon of water per person PER DAY on hand. Most people need 2 quarts of water per day for drinking. The other 2 quarts in the gallon per day are for cooking, bathing and cleaning. Don"t forget your pets. A small pet can drink one quart of water per day.
A large supply of stored water is bulky and not practical for everyone. One gallon of water weighs about 8 ½ pounds. Many local pandemic flu plans have water system restoration as a top priority, although it may not be purified. If you cannot store three months of drinking water, do these two things:
Of the two, water purification capability is the most important. Good drinking water will be needed during and between each pandemic wave.