Preparedness authorities like FEMA recommend storing at least 14 gallons of water per person. Storing that much will allow each person to use one gallon a day for two weeks. A family of four would want to store approximately 56 gallons of water (remember to store both stationary and portable). Keep in mind that this recommendation is for a minimum amount of water—just enough for drinking and light sanitation. To use water for cooking, bathing, or other needs, you’ll want to store more.