Drinking water

Drinking water that is supplied through a tap (tap water)

Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often supplied through taps, in which case it is also called tap water.

The amount of drinking water required to maintain good health varies, and depends on physical activity, age, health-related issues, and environmental conditions.[1][2] For those who work in a hot climate, up to 16 liters (4.2 U.S. gal) a day may be required.[1]

As many as two billion people lack safe drinking water.[3] Water can carry vectors of disease and is a major cause of death and illness worldwide.[4] Developing countries are most affected by unsafe drinking water.

Drinking water vending machines in Thailand. One liter of potable water is sold (into the customer's own bottle) for 1 baht. Diagram of water well types Simplified diagram of a water supply network

Potable water is available in almost all populated areas of the world, although it may be expensive, and the supply may not always be sustainable. Sources where drinking water is commonly obtained include springs, hyporheic zones and aquifers (groundwater), from rainwater harvesting, surface water (from rivers, streams, glaciers), or desalinated seawater.

For these water sources to be consumed safely, they must receive adequate water treatment and meet drinking water quality standards.[5]

An experimental source is solar-powered atmospheric water generators.[6]

Springs are often used as sources for bottled waters.[7]

The most efficient and convenient way to transport potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems.[8]

Tap water, delivered by domestic water systems refers to water piped to homes and delivered to a tap or spigot.

In the United States, the typical water consumption per capita, at home, is 69.3 U.S. gallons (262 L; 57.7 imp gal) of water per day.[9][10] Of this, only 1% of the water provided by public water suppliers is for drinking and cooking.[11] Uses include (in decreasing order) toilets, washing machines, showers, baths, faucets, and leaks.

Total renewable water resources per capita in 2020

The qualitative and quantitative aspects of drinking water requirements on domesticated animals are examined within the context of animal husbandry. For example, a farmer might plan for 35 U.S. gallons (130 L) per day for a dairy cow, a third of that for a horse, and a tenth of that for a hog.[15]

However, relatively few studies have been focused on the drinking behavior of wild animals.

Countries where tap water is safe to drink (blue)

According to a 2017 World Health Organization report, safe drinking water is water that "does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages".[16]: 2 

According to a report by UNICEF and UNESCO, Finland has the best drinking water quality in the world.[17][18]

Parameters for drinking water quality typically fall within three categories: microbiological, chemical and physical.

Microbiological parameters include coliform bacteria, E. coli, and specific pathogenic species of bacteria (such as cholera-causing Vibrio cholerae), viruses and protozoan parasites. Originally, fecal contamination was determined with the presence of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like E. Coli) serves as an indication of contamination by sewage. Additional contaminants include protozoan oocysts such as Cryptosporidium sp., Giardia lamblia, Legionella, and viruses (enteric).[19] Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.

Example for physical and chemical parameters measured in drinking water samples in Kenya and Ethiopia as part of a systematic review of published literature[20]

Physical and chemical parameters include heavy metals, trace organic compounds, total suspended solids and turbidity. Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and arsenic can have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.

Pesticides are also potential drinking water contaminants of the category chemical contaminants. Pesticides may be present in drinking water in low concentrations, but the toxicity of the chemical and the extent of human exposure are factors that are used to determine the specific health risk.[21]

Perfluorinated alkylated substances (PFAS) are a group of synthetic compounds used in a large variety of consumer products, such as food packaging, waterproof fabrics, carpeting and cookware. PFAS are known to persist in the environment and are commonly described as persistent organic pollutants. PFAS chemicals have been detected in blood, both humans and animals, worldwide, as well as in food products, water, air and soil.[22] Animal testing studies with PFAS have shown effects on growth and development, and possibly effects on reproduction, thyroid, the immune system and liver.[23] As of 2022 the health impacts of many PFAS compounds are not understood. Scientists are conducting research to determine the extent and severity of impacts from PFAS on human health.[24] PFAS have been widely detected in drinking water worldwide and regulations have been developed, or are under development, in many countries.[25]The U.S. Environmental Protection Agency (EPA) has published laboratory test methods for PFAS compounds.[26]