Drinking water (United States)

Public Drinking Water Systems

The United States is fortunate to have one of the safest public drinking water supplies in the world.

Find out about your local water quality:

Pennsylvania Department of Environmental Protection, Office of Water Management

West Virginia Department of Environmental Protection, Division of Water and Waste Management

U.S. Environmental Protection Agency's Office of Water

Public Water Systems Fast Facts

According to the United States Environmental Protection Agency (EPA)

  • Of the approximately 155,693 public water systems in the United States, 52,110 (33.5%) are community systems and 103,583 (66.5%) are noncommunity systems, including 84,744 transient systems and 18,839 nontransient systems. 
  • Over 286 million Americans get their tap water from a community water system.
  • 8% of U.S. community water systems provide water to 82% of the U.S. population through large municipal water systems.
  • Although the majority of community water systems (78%) are supplied by ground water, more people (68%) are supplied year-round by community water systems that use surface water.

Public drinking water systems consist of community and non-community systems.

Public Drinking Water Systems

  • A community water system (CWS) supplies water to the same population year-round. It serves at least 25 people at their primary residences or at least 15 residences that are primary residences (for example, municipalities, mobile home park, sub-divisions).
  • Non-community water systems are composed of transient and non-transient water systems.
  • Transient non-community water systems (TNCWS) provide water to 25 or more people for at least 60 days/year, but not to the same people and not on a regular basis (for example, gas stations, campgrounds).
  • Non-transient non-community water systems (NTNCWS) regularly supply water to at least 25 of the same people at least six month per year, but not year-round (for example, schools, factories, office buildings, and hospitals which have their own water systems).

The EPA is responsible for the nation's drinking water regulation. To learn more, visit the EPA's Public Drinking Water Systems page.

Top Causes of Public Drinking Water Outbreaks

According to the Centers for Disease Control and Prevention

  • Giardia -  is a microscopic parasite that causes the diarrheal illness known as giardiasis. Giardia(also known as Giardia intestinalis, Giardia lamblia, or Giardia duodenalis) is found on surfaces or in soil, food, or water that has been contaminated with feces (poop) from infected humans or animals. [more]
  • Ligionella - Legionnaires' disease (LEE-juh-nares) is caused by a type of bacterium called Legionella(LEE-juh-nell-a). The bacterium is named after a 1976 outbreak, when many people who went to a Philadelphia convention of the American Legion suffered from this disease, a type of pneumonia (lung infection). A milder infection, also caused by Legionella bacteria, is called Pontiac fever. The term "legionellosis" (LEE-juh-nuh-low-sis) may be used to refer to either Legionnaires' disease or Pontiac fever. [more]
  • Norovirus - Norovirus is a very contagious virus. You can get norovirus from an infected person, contaminated food or water, or by touching contaminated surfaces. The virus causes your stomach or intestines or both to get inflamed (acute gastroenteritis). This leads you to have stomach pain, nausea, and diarrhea and to throw up. Anyone can be infected with norovirus and get sick. Also, you can have norovirus illness many times in your life. Norovirus illness can be serious, especially for young children and older adults. [more]
  • Shigella - Shigellosis is an infectious disease caused by a group of bacteria called Shigella. Most who are infected with Shigella develop diarrhea, fever, and stomach cramps starting a day or two after they are exposed to the bacteria. The diarrhea is often bloody. Shigellosis usually resolves in 5 to 7 days. Persons with shigellosis in the United States rarely require hospitalization. A severe infection with high fever may be associated with seizures in children less than 2 years old. Some persons who are infected may have no symptoms at all, but may still pass the Shigella bacteria to others. [more]
  • Campylobacter - Campylobacteriosis is an infectious disease caused by bacteria of the genus Campylobacter. Most people who become ill with campylobacteriosis get diarrhea, cramping, abdominal pain, and fever within two to five days after exposure to the organism. Campylobacter is one of the most common causes of diarrheal illness in the United States. Most cases occur as isolated, sporadic events, not as part of recognized outbreaks. Active surveillance through the Foodborne Diseases Active Surveillance Network (FoodNet) indicates that about 14 cases are diagnosed each year for each 100,000 persons in the population. Many more cases go undiagnosed or unreported, and campylobacteriosis is estimated to affect over 1.3 million persons every year. Campylobacteriosis occurs much more frequently in the summer months than in the winter. [more]
  • Copper - Copper is a metal that occurs naturally in the environment, and also in plants and animals. Low levels of copper are essential for maintaining good health. However, high levels can cause harmful effects such as irritation of the nose, mouth and eyes, vomiting, diarrhea, stomach cramps, nausea, and even death. Copper has been found in at least 906 of the 1,647 National Priority Sites identified by the Environmental Protection Agency (EPA). [more]
  • Salmonella - Salmonellosis is an infection with bacteria called Salmonella. Salmonella germs have been known to cause illness for over 100 years. They were discovered by an American scientist named Salmon, for whom they are named. Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment. However, in some persons, the diarrhea may be so severe that the patient needs to be hospitalized. In these patients, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites and can cause death unless the person is treated promptly with antibiotics. The elderly, infants, and those with impaired immune systems are more likely to have a severe illness. [more]
  • Hepatitis A - Hepatitis A is a liver disease that results from infection with the Hepatitis A virus. It can range in severity from a mild illness lasting a few weeks to a severe illness lasting several months. Hepatitis A is usually spread when a person ingests fecal matter — even in microscopic amounts — from contact with objects, food, or drinks contaminated by the feces or stool of an infected person. [more]
  • Cryptosporidium -  Cryptosporidium is a microscopic parasite that causes the diarrheal disease cryptosporidiosis. Both the parasite and the disease are commonly known as "Crypto." There are many species of Cryptosporidium that infect humans and animals. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very tolerant to chlorine disinfection. While this parasite can be spread in several different ways, water (drinking water and recreational water) is the most common method of transmission. Cryptosporidium is one of the most frequent causes of waterborne disease among humans in the United States. [more]
  • E.Coli - Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coliare harmless and actually are an important part of a healthy human intestinal tract. However, some E. coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract. The types of E. coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons. [more]

For a complete listing of water-related surveillance data, see CDC’s Surveillance Reports for Drinking Water-associated Disease & Outbreaks.