How long could a human survive with 20 gallons of water?

A human can typically survive without water for about 3 to 7 days, depending on factors like climate, activity level, and individual health. With 20 gallons of water, a person could potentially survive much longer, as the average daily water intake for an adult is about 2 to 3 liters (roughly half a gallon). Therefore, 20 gallons could sustain one person for several weeks, assuming no other sources of hydration and moderate conditions. However, it's important to note that excessive water intake in a short period can also lead to health issues like water intoxication.