drinking water drinking water drinking water is water that is used in drink or food preparation; 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. recent work showed that the most important driver of water turnover which is closely linked to water requirements is energy expenditure. for those who work in a hot climate, up to 16 litres (4.2 us gal) a day may be required. typically in developed countries, tap water meets drinking water quality standards, even though only a small proportion is actually consumed or used in food preparation. other typical uses for tap water include washing, toilets, and irrigation. greywater may also be used for toilets or irrigation. its use for irrigation however may be associated with risks. water may also be unacceptable due to levels of toxins or suspended solids. tap water is drinking water supplied through plumbing for home use in many countries. globally, by 2015, 89% of people had access to water from a source that is suitable for drinking – called improved water source. in sub-saharan africa, access to potable water ranged from 40% to 80% of the population. nearly 4.2 billion people worldwide had access to tap water, while another 2.4 billion had access to wells or public taps. the world health organization considers access to safe drinking-water a basic human right. about 1 to 2 billion people lack safe drinking water. water can carry vectors of disease. more people die from unsafe water than from war, then-u.n. secretary-general ban ki-moon said in 2010. third world countries are most affected by lack of water, flooding, and water quality. up to 80 percent of illnesses in developing countries are the direct result of inadequate water and sanitation. according to a report by unicef and unesco, finland has the best drinking water quality in the world. water resources further information: water resources and water security drinking water vending machines in thailand. one litre 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 water covers approximately 70% of the earth's surface, where approximately 97.2% of it is saline, only 2.8% fresh. potable water is available in almost all populated areas of the earth, although it may be expensive and the supply may not always be sustainable. sources where water may be obtained include springs, hyporheic zones and aquifers, and: precipitation which includes rain, hail, snow, fog, etc. surface water such as rivers, streams, glaciers biological sources such as plants desalinated seawater water supply network atmospheric water generators threats for the availability of water resources include: water scarcity, water pollution, water conflict, insufficient well-depth, droughts and overpumping, and the effects of climate change. consumption requirements for drinking main article: fluid balance the amount of drinking water required per day is variable. it depends on physical activity, age, health, and environmental conditions. in the united states, the adequate intake for total water, based on median intakes, is 3.7 litres (130 imp fl oz; 130 us fl oz) per day for human males older than 18, and 2.7 litres (95 imp fl oz; 91 us fl oz) per day for human females older than 18 which includes about 80% from beverages and 20% from food. the european food safety authority recommends 2.0 litres (70 imp fl oz; 68 us fl oz) of total water per day for adult women and 2.5 litres (88 imp fl oz; 85 us fl oz) per day for adult men. the common advice to drink 8 glasses (1,900 ml or 64 us fl oz) of plain water per day is not based on science, and an individual's thirst provides a better guide for how much water they require rather than a specific, fixed quantity. americans age 21 and older, on average, drink 1,043 ml (36.7 imp fl oz; 35.3 us fl oz) of drinking water a day and 95% drink less than 2,958 ml (104.1 imp fl oz; 100.0 us fl oz) per day. physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake. physically active individuals in hot climates may have total daily water needs of 6 litres (210 imp fl oz; 200 us fl oz) or more. the drinking water contribution to mineral nutrients intake is also unclear. inorganic minerals generally enter surface water and ground water via storm water runoff or through the earth's crust. treatment processes also lead to the presence of some minerals. examples include calcium, zinc, manganese, phosphate, fluoride and sodium compounds. water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. there are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. for example, sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role in body metabolism. other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels. fluid balance is key. profuse sweating can increase the need for electrolyte (salt) replacement. water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal. water makes up about 60% of the body weight in men and 55% of weight in women. a baby is composed of about 70% to 80% water while the elderly are composed of around 45%. household usage in the united states, the typical water consumption per capita, at home, is 69.3 us gallons (262 l; 57.7 imp gal) of water per day. of this, only 1% of the water provided by public water suppliers is for drinking and cooking. uses include (in decreasing order) toilets, washing machines, showers, baths, faucets, and leaks. animals the qualitative and quantitative aspects of drinking water requirements on domesticated animals are studied and described within the context of animal husbandry. however, relatively few studies have been focused on the drinking behavior of wild animals. water supply main article: water supply the most efficient and convenient way to transport and deliver 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. springs are often used as sources for bottled waters. tap water, delivered by domestic water systems refers to water piped to homes and delivered to a tap or spigot. for these water sources to be consumed safely, they must receive adequate treatment and meet drinking water regulations. because of the high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water. 2003 statistics from el salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. in the united kingdom, authorities define spending of more than 3% of one's income on water as a hardship. water quality main articles: water quality, drinking water quality standards, and water pollution where you can drink tap water around the world epa drinking water security poster from 2003 according to the world health organization's 2017 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".: 2 parameters for drinking water quality typically fall within three categories: physical, chemical, microbiological. 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. 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). microbial pathogenic parameters are typically of greatest concern because of their immediate health risk. throughout most of the world, the most common contamination of raw water sources is from human sewage in particular human fecal pathogens and parasites. in 2006, waterborne diseases were estimated to cause 1.8 million deaths while about 1.1 billion people lacked proper drinking water. in parts of the world, the only sources of water are from small streams that are often directly contaminated by sewage. pesticides, whether used in agriculture or domestically (e.g. homes, schools, businesses) are potential drinking water 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. 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. animal testing studies with pfas have shown effects on growth and development, and possibly effects on reproduction, thyroid, the immune system and liver. 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. pfas have been widely detected in drinking water worldwide and regulations have been developed, or are under development, in many countries. water treatment main articles: water purification and water treatment water treatment plant most water requires some treatment before use; even water from deep wells or springs. the extent of treatment depends on the source of the water. appropriate technology options in water treatment include both community-scale and household-scale point-of-use (pou) designs. only a few large urban areas such as christchurch, new zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required. in emergency situations when conventional treatment systems have been compromised, waterborne pathogens may be killed or inactivated by boiling but this requires abundant sources of fuel, and can be very onerous on consumers, especially where it is difficult to store boiled water in sterile conditions. other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar uv) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries, but these suffer from the same problems as boiling methods. another type of water treatment is called desalination and is used mainly in dry areas with access to large bodies of saltwater. point of use methods main articles: portable water purification and self-supply of water and sanitation the ability of point of use (pou) options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest. the current priority of the proponents of pou treatment is to reach large numbers of low-income households on a sustainable basis. few pou measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.