Current recommendations for stored water are a minimum of 14 gallons/person, enough for about 2 weeks. National emergency authorities recommend changing and replacing your stored tap water every 6 months. It’s easy to remember to do this in the spring and again in the fall.
FEMA and the American Red Cross say pre-treating tap water that is treated commercially by a water treatment facility with bleach will not increase its storage life and is not necessary. If you store water from a well, or public water that is not treated, follow instructions provided by your local public health authority or water provider.