Potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies and depends on physical activity level, age, health-related issues, and environmental conditions. For those who work in a hot climate, up to 4.2 US gal a day may be required. In developed countries, tap water meets drinking water quality standards, even though only a small proportion is consumed or used in food preparation.

Source: Wikipedia