The Safe Drinking Water Act (SDWA) is the main federal law in the United States that ensures safe drinking water for the public. According to the SDWA, the Environmental Protection Agency (EPA) must set standards for drinking water quality and supervise all states, local areas, and water suppliers who follow these standards.

The SDWA applies to every public water system (PWS) in the United States. There are currently more than 148,000 public water systems that provide water to nearly all Americans at some point in their lives. The Act does not cover private wells. In 2020, 13% of U.S. households used private wells for their water.

The SDWA does not apply to bottled water. Bottled water is regulated by the Food and Drug Administration (FDA) under the Federal Food, Drug, and Cosmetic Act.

National Primary Drinking Water Regulations

The Safe Drinking Water Act (SDWA) requires the Environmental Protection Agency (EPA) to create National Primary Drinking Water Regulations (NPDWRs) for substances that could harm public health. These regulations include rules that must be followed, such as Maximum Contaminant Levels (MCLs) and Treatment Techniques, and goals that guide health standards but are not legally enforceable, called Maximum Contaminant Level Goals (MCLGs). As of 2019, the EPA has set 88 standards for microorganisms, chemicals, and radionuclides.

MCLs are important because they can be used in the Superfund law as "Applicable or Relevant and Appropriate Requirements" for cleaning up polluted sites on the National Priorities List. For some substances, the EPA sets Treatment Techniques (TTs) instead of MCLs. TTs are rules that drinking water systems must follow to treat water for specific contaminants.

Federal drinking water standards are grouped into six categories:
• Microorganisms
• Disinfectants
• Disinfection byproducts
• Inorganic chemicals
• Organic chemicals
• Radionuclides

The EPA has set standards for Cryptosporidium, Giardia lamblia, Legionella, coliform bacteria, and enteric viruses. The agency also requires two tests to check water quality: plate count and turbidity. The Surface Water Treatment Rule, first introduced in 1989, addressed contamination from viruses, bacteria, and Giardia lamblia. The most recent update, the Long Term 2 Enhanced Surface Water Treatment Rule (2006), requires public water systems to use Treatment Techniques to control Cryptosporidium and other pathogens.

The EPA has set standards for chlorine, monochloramine, and chlorine dioxide. It also has standards for bromate, chlorite, haloacetic acids, and trihalomethanes. Standards cover inorganic chemicals such as antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, copper, cyanide, fluoride, lead, mercury, nitrate, nitrite, selenium, and thallium.

The 1986 amendments require the EPA to set rules limiting lead in public water systems. The law defines "lead free" pipes as those with very low lead content. The EPA introduced its first lead and copper regulation in 1991, which required a Treatment Technique instead of an MCL. In 2011, Congress updated the definition of "lead free" plumbing. The EPA finalized a rule implementing this change on September 1, 2020.

In response to the Flint, Michigan water crisis, the EPA revised the Lead and Copper Rule on January 15, 2021, to improve testing, pipe replacement, and public communication. The rule requires more detailed sampling of tap water, better corrosion control, and testing in schools. After legal challenges, the EPA finalized the "Lead and Copper Rule Improvements" on October 8, 2024. This rule requires removing all lead pipes within ten years and lowers the action level for lead contamination to 10 parts per billion (ppb) from the previous limit of 15 ppb.

The EPA has set standards for over 53 organic compounds, including benzene, dioxin (2,3,7,8-TCDD), PCBs, styrene, toluene, vinyl chloride, and several pesticides. In March 2021, the EPA announced plans to regulate perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). In April 2024, the EPA finalized standards for PFOA, PFOS, perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (GenX), and perfluorobutanesulfonic acid (PFBS). The agency is offering grants to help small and disadvantaged communities test for and treat PFAS contamination in their water.

The EPA has set standards for alpha particles, beta particles, photon emitters, radium, and uranium. The agency proposed rules for radon in 1991 and 1999.

Secondary standards

Secondary drinking water standards are guidelines that are not legally required. They focus on the appearance, taste, and smell of water, which affect how it looks, tastes, or smells.

Health advisories

The Environmental Protection Agency (EPA) releases "health advisories" for certain contaminants that are not controlled by Maximum Contaminant Levels (MCLs). These advisories give public health officials details about health effects, how to test for chemicals, and ways to treat water. Health advisories are not legally required. The EPA received clear permission to issue advisories through changes made to the Safe Drinking Water Act in 1996. In 2022, health advisories were issued for the following contaminants.

State standards

The Safe Drinking Water Act (SDWA) lets states create rules that are stricter than the rules set by the federal government. It also allows states to create rules for pollutants that the Environmental Protection Agency (EPA) has not yet controlled. Some states have created their own rules for certain pollutants, such as fluoride, perchlorate, and perfluorinated alkylated substances (PFAS).

Future standards

The Safe Drinking Water Act (SDWA) requires the Environmental Protection Agency (EPA) to find and list unregulated contaminants that might need rules. The EPA must publish this list, called the Contaminant Candidate List (CCL), every five years. The EPA must decide whether to create rules for at least five or more listed contaminants. The list helps the EPA plan research and data collection to support decisions about regulations.

As of 2024, the EPA has created five CCLs:

• CCL1: In 1998, the list included 50 chemical and 10 microbiological contaminants. In 2003, the EPA decided no rules were needed for nine of these contaminants.
• CCL2: In 2005, the EPA continued to consider the remaining 51 contaminants from CCL1. In 2008, the EPA decided no rules were needed for 11 of these contaminants.
• CCL3: The EPA changed its process for selecting contaminants based on advice from two groups. It first reviewed 7,500 possible chemical and microbial contaminants and later narrowed the list to 600 for further study. In 2009, the list included 104 chemicals or chemical groups and 12 microbiological contaminants. In 2011, the EPA decided to create rules for perchlorate, which had been on CCL1. In 2016, the EPA decided no rules were needed for four other contaminants and delayed a decision on a fifth to review more data.
• CCL4: The EPA continued to consider contaminants from CCL3 for which no decisions had been made and asked the public for feedback on additional contaminants. In 2016, the list included 97 chemicals or chemical groups and 12 microbial contaminants. In March 2021, the EPA announced it would create rules for two CCL4 contaminants: PFOA and PFOS.
• CCL5: In November 2022, the EPA published the fifth CCL. The list includes 66 chemicals, three chemical groups (including PFAS), and 12 microbes.

In 2023, the EPA asked the public for feedback on a draft of the sixth CCL.

On December 27, 2021, the EPA published a rule requiring drinking water utilities to monitor for 29 PFAS compounds and lithium. Data collection will happen between 2023 and 2025. The EPA will pay for monitoring costs for small drinking water systems (those serving 10,000 people or fewer). The agency may use the data to create more rules.

In 2016, the Natural Resources Defense Council (NRDC) sued the EPA to speed up the rulemaking process for perchlorate. After a court agreement, the EPA proposed a rule in June 2019 with a suggested maximum contaminant level (MCL) of 0.056 mg/L.

In 2020, the EPA canceled its 2019 proposal and its 2011 decision, saying it had worked with state and local governments to address perchlorate contamination. In September 2020, NRDC sued the EPA again for failing to regulate perchlorate, noting that 26 million people might be affected by perchlorate in their drinking water. After a court order, the EPA proposed a rule for perchlorate on January 6, 2026. The court requires the EPA to finalize the rule by 2027.

Monitoring, compliance and enforcement

Public water systems must regularly check their water for harmful substances. Water samples must be tested using methods approved by the EPA, and the testing must be done by labs that are certified by the EPA or a state agency.

A public water system must inform its customers if it breaks drinking water rules or if the water may harm health. These notices are sent right away, as soon as possible (but no later than 30 days after the problem) or once a year, depending on the health risk. Community water systems, which serve the same people all year, must give an annual "Consumer Confidence Report" to customers. This report lists any harmful substances found in the water and explains what health risks they might cause.

The Public Water System Supervision Program includes "primacy" agencies, which are state governments, Native American tribes, or EPA offices. All states and territories, except Wyoming and the District of Columbia, have been approved by the EPA to oversee public water systems in their areas. A public water system must send regular monitoring reports to its primacy agency. If a system breaks Safe Drinking Water Act rules, the primacy agency first sends a notice to the system. If needed, the agency may also issue official orders and fines.

Protection of Underground Sources of Drinking Water

An underground source of drinking water (USDW) is an underground water source that has enough clean water to supply public water systems now or in the future.

The Safe Drinking Water Act (SDWA) forbids any underground injection that could harm drinking water sources. A court explained that even injecting clean water underground can accidentally move harmful substances into an USDW, which is illegal.

The SDWA, passed in 1974, allowed the Environmental Protection Agency (EPA) to regulate injection wells to protect USDWs. The Underground Injection Control (UIC) permit system divides wells into six classes:

• Class I: Wells that dispose of industrial waste (both harmful and non-harmful) and wastewater from cities.
• Class II: Wells related to oil and gas production, except those used only for hydraulic fracturing.
• Class III: Wells used for solution mining.
• Class IV: Wells for shallow disposal of hazardous or radioactive waste (no longer allowed).
• Class V: Wells that inject non-harmful fluids into or above USDWs.
• Class VI: Wells used to store carbon dioxide underground for long-term storage.

The EPA has given 34 states the authority to enforce UIC rules for Classes I, II, III, IV, and V. Seven states and two tribes have authority to enforce rules for Class II wells only. The EPA directly manages enforcement for Class VI wells.

If a state fails to take action against violations, the EPA must issue an order to correct the problem or start a legal case. The SDWA allows people to take legal action if the EPA or a violator does not follow the law.

In 2005, Congress changed the SDWA to exclude hydraulic fracturing from UIC rules, except when diesel fuel is used. This change is called the "Halliburton Loophole," named after Halliburton, a major company that provides hydraulic fracturing services. This change followed a recommendation from a group led by Vice President Dick Cheney, who had previously worked for Halliburton.

The law requires states to create wellhead protection programs to protect USDWs. These programs must define the roles of agencies, identify areas around wells that need protection, find sources of pollution, create plans to stop pollution, and prepare backup water supplies in case of contamination. Federal agencies must follow state wellhead protection rules.

A guidance document explains that the EPA Administrator has the power to act quickly to protect USDWs and public water systems if there is a risk to health. This power applies to all USDWs, including future water supplies and private wells. The EPA can act even without full proof if harmful substances, such as lead or cancer-causing chemicals, may cause long-term harm.

If the EPA finds a UIC violation and the state cannot or will not act, the EPA must issue an order or start a legal case to enforce the rules.

Citizens can file a lawsuit to challenge the EPA’s final decisions. They can also sue violators of the SDWA or the EPA if it fails to act on matters that are not optional. The EPA’s emergency orders are also subject to legal review.

Related programs

In 2004, the Environmental Protection Agency (EPA) tested drinking water on airplanes and found that 15% of the tested aircraft had bacteria that can cause illness. In 2009, the EPA created rules requiring airlines operating in the United States to check for bacteria in their water systems. These rules also require airlines to follow safe water practices, fix problems if bacteria are found, inform the public about water quality, train workers, and keep records of their actions. If an airline fails to follow these rules, it must stop allowing passengers to use the on-board water system for a set amount of time.

The Safe Drinking Water Act (SDWA) requires each state to draw boundaries around areas where public water systems take water from, including both surface water (like lakes and rivers) and underground water sources. Within these areas, the sources of harmful substances are identified to help determine how likely it is that these substances could enter the water supply. This information helps communities understand possible risks to their drinking water.

The SDWA also includes a rule to protect workers who report violations of the law. If someone in the United States believes they were fired or faced another negative action because they reported a problem related to this law, they have 30 days to write a complaint to the Occupational Safety and Health Administration (OSHA).

History

Before the Safe Drinking Water Act (SDWA) was passed, there were few national rules that required clean drinking water. In 1914, the U.S. Public Health Service (PHS) created drinking water standards under federal laws that regulated business between states and in response to a law from 1893. These standards only applied to large transportation companies, like railroads, that moved goods across state lines. For local water systems, the standards were suggestions, not rules. However, many cities chose to follow them anyway.

In the 1960s and early 1970s, people became more worried about health problems caused by dirty drinking water. Reports showed that bacteria and viruses in public water systems led to illnesses like cancer and stomach problems. When harmful chemicals like lead and synthetic chemicals were found in drinking water, public concern grew. More people were using water resources because of growing cities and more people, which made water contamination more likely. Scientists, health workers, and environmental groups pushed Congress to create national drinking water rules.

In the 1970s, better testing methods helped find small amounts of harmful chemicals in water. Some water managers thought the biggest problems were already solved and focused on keeping water clean from bacteria.

On January 3, 1973, a bill for the Safe Drinking Water Act was introduced in the House of Representatives by Paul Rogers. A similar bill was introduced in the Senate on January 18, 1973. The bill went through many steps, including hearings and votes, before President Gerald Ford signed it into law on December 16, 1974.

The Safe Drinking Water Act was one of many environmental laws passed in the 1970s. Scientists found harmful chemicals in public water systems and saw the need for national rules. The 1974 law clearly defined roles, giving the Environmental Protection Agency (EPA) the task of creating scientific standards for water supplies serving 25 or more people. The EPA worked with the National Academy of Sciences to study harmful chemicals and set rules based on their findings.

The EPA created a system to protect public health by identifying dangerous contaminants like lead and bacteria and enforcing limits on them. The agency set health-based goals for contaminant levels and created legally binding limits that balanced health needs with the cost of water treatment. The EPA also required regular water testing, public reports about water quality, and education campaigns to help communities understand water safety. The EPA worked with state and local governments to improve water systems and ensure long-term clean water access.

In 1986, the SDWA was updated to require the EPA to apply new drinking water rules to both community and non-transient non-community water systems. This change was first used in 1987 for rules about certain harmful chemicals. The 1986 updates were signed into law by President Ronald Reagan. These updates also included requirements like protecting water well areas, testing for new substances, filtering surface water, disinfecting groundwater, limiting lead in plumbing, and giving the EPA more power to enforce rules.

In 1996, the SDWA was updated again to focus on science-based rules, help small water systems, and improve water safety. These changes included:
1. Consumer Confidence Reports: All community water systems must share yearly reports about water quality, including contaminants found, health risks, and water sources.
2. Cost-Benefit Analysis: The EPA must study the costs and benefits of new rules to ensure they are worth the effort.
3. Drinking Water State Revolving Fund: States can use this fund to help improve water systems, protect water sources, or upgrade infrastructure.
4. Microbial Contaminants and Disinfection Byproducts: The EPA must strengthen rules to protect against harmful microbes like cryptosporidium and control harmful byproducts from water treatment chemicals.
5. Operator Certification: Water system workers must be trained and certified to ensure safe water operations.

Environmental justice

The Safe Drinking Water Act (SDWA) can help protect the environment by making drinking water safer for communities most affected by water pollution. In the United States, communities of color and low-income communities are more likely to experience unsafe drinking water and related health issues. Native American reservations and areas with large Latino and African American populations are especially at risk of being exposed to harmful substances in drinking water. These substances include nitrates, coliform, and lead, which are linked to cancer, problems with having children, stomach and intestinal illnesses, and other health issues. One study found that drinking water on two Native American reservations in Nebraska had much higher levels of contaminants than other areas in the region. Another study showed that Latino residents in Tucson, Arizona, had higher-than-average levels of contaminants in their drinking water, which were connected to higher rates of cancer and problems with the brain and nerves. It is also known that low-income residents in the Appalachian region of West Virginia face greater exposure to water contaminants caused by coal mining in the area.

When addressing the updated goals of the act, the EPA states that its first goal is to "promote fairness… in communities that are struggling, small, and those affected by environmental issues," focusing on helping these communities deal with the risks of contaminated drinking water.