Tap water (also called faucet water, tap water or municipal water) is water supplied through taps and drinking fountain valves. Tap water is usually used for drinking, cooking, washing and flushing toilets. Indoor tap water is distributed through “indoor pipes”. This type of pipe has existed since ancient times, but it was not provided to a handful of people until the second half of the 19th century when it began to become popular in today’s developed countries. Tap water became common in many regions in the 20th century and is now mainly lacking among the poor, especially in developing countries.

In many countries, tap water is usually related to drinking water. Government agencies usually supervise the quality of tap water. Household water purification methods, such as water filters, boiling or distillation, can be used to treat the microbial contamination of tap water to improve its drinkability.  The application of technologies (such as water treatment plants) that provide clean water to homes, businesses, and public buildings is a major subfield of sanitary engineering. Calling the water supply “tap water” distinguishes it from other major freshwater types that may be available; these include water from rainwater collection ponds, water from village or town pumps, water from wells, or streams, rivers, or lakes (The drinkability may vary) water.

background
Providing tap water to the population of large cities or suburbs requires a complex and well-designed collection, storage, processing, and distribution system, and is usually the responsibility of government agencies.

Historically, publicly available treated water has been associated with a significant increase in life expectancy and improvement in public health. Water disinfection can greatly reduce the risk of water-borne diseases such as typhoid fever and cholera. There is a great need for disinfection of drinking water all over the world. Chlorination is currently the most widely used method of water disinfection, although chlorine compounds can react with substances in the water and produce disinfection by-products (DBP) that cause problems for human health.The local geological conditions affecting groundwater are the decisive factors for the existence of various metal ions, which usually make the water “soft” or “hard”.

Tap water is still vulnerable to biological or chemical pollution. Water pollution is still a serious health problem worldwide. Diseases caused by drinking contaminated water kill 1.6 million children every year. If pollution is considered harmful to public health, government officials usually issue recommendations on water consumption. In the case of biological contamination, it is usually recommended that residents boil water or use bottled water as an alternative before drinking. In the case of chemical pollution, residents may be advised to avoid drinking tap water completely until the problem is resolved.

In many areas, low concentrations of fluoride (< 1.0 ppm F) are intentionally added to tap water to improve dental health, although “fluoridation” is still a controversial issue in some communities. (See the water fluorination controversy). However, long-term drinking of water with high fluoride concentration (> 1.5 ppm F) can have serious adverse consequences, such as dental fluorosis, enamel plaque and skeletal fluorosis, and bone deformities in children. The severity of fluorosis depends on the fluoride content in the water, as well as people’s diet and physical activity. Fluoride removal methods include membrane-based methods, precipitation, absorption, and electrocoagulation.

Regulation and compliance
America
The U.S. Environmental Protection Agency (EPA) regulates the allowable levels of certain pollutants in public water supply systems. Tap water may also contain many pollutants that are not regulated by EPA but may be harmful to human health. Community water systems—those that serve the same group of people throughout the year—must provide customers with an annual “consumer confidence report.” The report identifies the pollutants (if any) in the water system and explains the potential health effects.  After the Flint Lead Crisis (2014), researchers paid special attention to the study of drinking water quality trends across the United States. Unsafe levels of lead have been found in tap water in different cities, such as Sebring, Ohio in August 2015 and Washington, DC in 2001 . Multiple studies have shown that, on average, about 7-8% of community water systems (CWS) violate the Safe Drinking Water Act (SDWA) health issues every year. Due to the presence of pollutants in drinking water, there are approximately 16 million cases of acute gastroenteritis in the United States each year.

Before constructing or modifying the water supply system, designers and contractors must consult local plumbing codes and obtain construction permits before construction.  Replacing an existing water heater may require a permit and a work inspection. The national standard of the U.S. Drinking Water Pipeline Guide is a material certified by NSF/ANSI 61. NSF/ANSI also established standards for the certification of multiple cans, although the Food and Drug Administration (FDA) approved these materials.