Drinking water or potable water is water of sufficiently high quality that can be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually consumed or used in food preparation.
Over large parts of the world, humans have inadequate access to potable water and use sources contaminated with disease vectors, pathogens or unacceptable levels of toxins or suspended solids. Such water is not potable, and drinking or using such water in food preparation leads to widespread acute and chronic illnesses and is a major cause of death and misery in many countries. Reduction of waterborne diseases is a major public health goal in developing countries.
Typical water supply networks deliver potable water from the tap, whether it is to be used for drinking, washing or landscape irrigation. One counterexample is urban China, where drinking water can optionally be delivered by a separate tap, often in the form of distilled water or otherwise the regular tap water needs to be boiled.
Water has always been an important and life-sustaining drink to humans and is essential to the survival of all organisms. Excluding fat, water composes approximately 70% of the human body by mass. It is a crucial component of metabolic processes and serves as a solvent for many bodily solutes. Health authorities have historically suggested at least eight glasses, eight fluid ounces each (240 ml), of water per day (64 fluid ounces, or 1.89 litres), and the British Dietetic Association recommends 1.8 litres. The United States Environmental Protection Agency in risk assessment calculations assumes that the average American adult ingests 2.0 litres per day.