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Drinking Water

Issue Summary
Drinking Water Standards
Unregulated Contaminants
Variances and Exemptions
Monitoring and Reporting
Lead and Copper Rule
State Programs, Enforcement and Compliance Assistance
Tribes and Treatment as a State
Source Water Protection
Underground Injection Control Program
Water Reuse
Organizations/Non-Government Programs


Issue Summary

The Safe Drinking Water Act (SDWA) protects public water supplies primarily by establishing minimum water quality standards for contaminants that the nation's nearly 50,000 public water systems must meet, as well as monitoring and reporting obligations. The SDWA additionally provides for technical assistance to small water systems, controlling the underground injection of fluids, financing infrastructure projects and protecting sources of drinking water.

The SDWA applies to public water systems (PWS), which are water systems, whether owned and operated by government entities or private investors, that:

  • Supply, to the public, water for human consumption through pipes or other constructed conveyances, and
  • Provide at least 15 service connections, or regularly serve (meaning a minimum of 60 days out of the year) at least 25 individuals. 

The three broad categories of PWS regulated by the law are community water systems (CWS), most commonly associated with local water utilities, non-transient non-community water systems (NTNCWS) and transient non-community water systems (TNCWS).

EPA may delegate to states, territories, and Indian tribes primary implementation and enforcement authority (primacy) for the Public Water Supply Supervision (PWSS) Program and the underground injection control (UIJ) program. EPA has delegated PWSS authority to 49 states and one tribe (Navajo Nation); EPA retains a backup enforcement role and has emergency powers to protect public health. EPA is primarily responsible for enforcing drinking water requirements in Wyoming, Washington, DC and on most Indian reservations.

Drinking Water Standards

EPA regulates more than 90 contaminants under the SDWA. EPA sets both primary and secondary standards for contaminants.

The National Primary Drinking Water Regulations (NPDWR), or primary standards, protect public health. EPA establishes these for contaminants that: (1) may have adverse effects; (2) "are known to occur, or there is a substantial likelihood that they will occur in PWSs with a frequency and at levels of public health concern"; and (3) for which regulation could reduce health risks. EPA's process for establishing primary standards involves identifying contaminants of potential concern, assessing health risks, collecting national occurrence data and making a determination whether a contaminant warrants regulation. New standards take effect  three years after adoption by EPA, but a PWS may seek two additional years to comply if additional time is necessary for capital improvements. EPA reviews each primary standard every six years.

Secondary standards protect public welfare. They address aesthetic concerns, such as odor, taste and appearance. Secondary standards are not federally enforceable, but may be enforceable under state law.

For each regulated contaminant, EPA sets either a Maximum Contaminant Level (MCL) or a treatment technique. EPA first sets a non-enforceable Maximum Contaminant Level Goal (MCLG) at a level at which there are no known or anticipated adverse health effects, with an adequate margin of safety. The MCLG is set at zero for probable carcinogens and at a "no effect" level for noncarcinogenic contaminants. It is based on EPA's estimate of the general population's exposure to the contaminant that is attributable to drinking water. EPA then sets an enforceable MCL as close to the MCLG as is feasible for a PWS to attain with the use of the best technology available, taking costs into consideration. EPA does not specify any specific technology or method for meeting the MCL, but generally sets standards based on technologies that are affordable for large communities. EPA also lists methods that are affordable for small PWSs serving populations of 10,000 or fewer. A PWS may use any technology to meet the MCL, but cannot use bottled water, except in certain temporary circumstances. 

EPA will establish a treatment technique—an engineering or design requirement—in lieu of an MCL, if it is technologically or economically infeasible for a PWS to monitor for the contaminant in drinking water.

EPA may also promulgate an interim national primary drinking water regulation to address an urgent threat to public health.

Unregulated Contaminants

Many contaminants are unregulated. Every five years, EPA publishes the Contaminant Candidate List (click to see CCL 5), a list of unregulated contaminants that are known or anticipated to occur in PWSs and that may warrant regulation. 

Every five years, EPA also publishes an Unregulated Contaminant Monitoring Rule 

(see proposed UCMR 5). The UCMR lists no more than 30 unregulated contaminants each PWS will monitor. The goal is to assess the frequency and levels of a contaminant's occurrence nationwide and inform EPA's review of contaminants that may warrant regulation. All systems serving more than 10,000 people—and a nationally representative sample of smaller systems—must monitor for these contaminants. The data are added to the National Contaminant Occurrence Database

EPA has issued health advisories for more than 200 contaminants not regulated under SDWA. EPA sets health advisory levels at concentrations expected to be protective of the most sensitive subpopulations. Health advisories provide information on health effects, chemical properties, occurrence, exposure, test methods and treatment technologies for specific contaminants. 

Variances and Exemptions

A PWS may qualify for a temporary variance or exemption from meeting primary standards under certain conditions. Variances are authorized for source water quality issues, but only if the PWS installs an identified variance technology and if the resulting drinking water quality is protective of people's health. The PWS must follow a compliance schedule and notify the public of the variance. Exemptions give eligible systems additional time to achieve and maintain regulatory compliance with new primary standards. They apply only if a system cannot comply for other compelling reasons (including costs) and as long as the drinking water does not cause unreasonable risk to health. Similar to variances, a PWS must follow a compliance schedule and notify the public. Exemptions are effective for three years.


CWS operators must be certified. EPA provides reimbursement for costs of training and certification for persons operating systems serving 3,300 or fewer persons.

Monitoring and Reporting

A PWS must monitor its water supply to ensure compliance with the SDWA and report its monitoring results to the primary regulator. EPA establishes analytical test methods required for all prescribed monitoring activities.

Each PWS must directly notify customers about:

  • Any failure to comply with a primary standard or testing or monitoring requirements. Notice of violations or exceedances with the potential for serious adverse effects on human health must be issued within 24 hours of the PWS learning of the violation. The notice must contain clear explanations of the violation or exceedance, its potential adverse effects on human health, corrective steps the PWS is taking and the necessity of seeking alternative water supplies in the interim. Notice must also be provided to EPA, as well as the head of the state or tribal agency with primacy, and disseminated through the appropriate media

  • Existence of any variance or exemption, and any failure to comply with related requirements

  • The concentration level of any unregulated contaminant for which EPA requires public notice

Each CWS must also issue an annual Consumer Confidence Report (CCR). A CCR is an annual report on the level of contaminants in the drinking water (including specified lead action level exceedances), the results of UCMR monitoring, violations of primary standards and significant violations of monitoring requirements that occurred during the monitoring period. SDWA regulations detail what content a PWS must include in each CCR. 

Lead and Copper Rule

Exposure to lead or copper results in serious health impacts. Lead (Pb) can damage the brain, red blood, cells and kidneys, and is especially damaging to young children and pregnant women; there is no level of lead considered "safe." Copper (Cu) exposure results in stomach and intestinal distress, liver or kidney damage and complications of Wilson's disease in genetically predisposed people. Detecting and treating lead is particularly challenging, because it most often enters domestic water supplies after treated water enters the distribution system. Controlling corrosion is the principal method used to reduce lead in tap water, because lead can leach from pipes, plumbing materials and fixtures. Lead service lines (LSL) are a common culprit. Lead service lines were often used to extend water service from water mains to residences prior to the 1930s. EPA currently estimates between 6.3 and 9.3 million LSLs remain in service nationwide.

Direct regulation of lead under the SDWA

SDWA directly prohibits a PWS from using pipes, including solder and flux, that is not "lead free." This translates into an allowable standard of 0.25% lead weighted average for pipes, plumbing, fittings and fixtures. Solder and flux is limited to 0.2% lead. Exceptions exist for pipes, pipe fitting, plumbing fittings and fixtures that are used exclusively for nonpotable services, such as toilets, bidets, shower valves and fire hydrants. However, many communities and homes contain legacy pipes and plumbing exceeding this limit.

A PWS must notify the public, state and EPA of system lead action level exceedances (action levels explained below). A PWS must issue this notification within 24 hours for an exceedance that has the potential to cause serious adverse health effects from short-term exposure. If EPA has data indicating that a household's water exceeds the lead action level, it will forward the data and testing information to the water system and the state; the PWS then must provide the data and other specified information to the affected households.

Lead and Copper Rule (LCR)

The Lead and Copper Rule (LCR) is a treatment technique (not an MCL) for lead and copper. The LCR sets an action level (AL) based on the 90th percentile level of samples collected at consumers' taps in certain homes: 15 ppb for lead and 1,300 ppb for copper. An AL exceeded in samples collected at consumers' taps triggers the following actions.

  • Optimize corrosion control treatment (CCT). This usually involves adjusting the water supply's acidity. A CWS has 24 months to install the type of CCT selected by the state, followed by two consecutive six-month periods of tap sampling and water quality parameter monitoring. Medium and small systems may cease CCT if they maintain levels equal to or less than the AL for two consecutive six-month periods, but they must recommence if the AL is again exceeded.

  • Public education. The CWS must notify consumers of lead tap monitoring results, and notify both customers and the public within 60 days after the end of a monitoring period in which a lead AL level is exceeded. Notification is through quarterly water bill inserts, biennial press releases and information posted online. The LCR sets out requirements governing the content and delivery of printed public education materials (e.g., information on health effects of lead, sources of lead, steps consumers can take to reduce their exposure to lead and how to access water testing). A PWS must coordinate with local health agencies to reach at-risk populations and deliver materials to other organizations serving these populations.

  • Water quality parameter (WQP) monitoring. WQP samples at taps are collected every six months. WQP samples at entry points to the distribution system are collected every six months prior to CCT installation, and then every two weeks. 

  • Source water treatment (SOWT). Each state sets maximum permissible levels (MPLs) for Pb and Cu in source water and mandates the treatment method. Systems have 24 months to install the treatment, and then conduct follow-up monitoring. 

  • Lead service line replacement (LSLR). A CWS typically owns the portion of the service line extending from a water main to a residence's property line, a water meter, or a shut-off valve; the remaining portion is owned by the property owner. A CWS that has optimized corrosion control and still exceeds the lead AL is required to replace at least 7% of its LSLs annually until the AL is not exceeded for two consecutive six-month monitoring periods; the state can require an accelerated schedule. The CWS must replace the portion of each LSL it owns and offer owners an opportunity to have their portion of the LSL replaced at the owner's cost; a CWS is not required to pay for the owner's replacement costs. However, if the CWS only partially replaces a LSL, it must notify residents at least 45 days prior about potential for increased lead levels and inform them about measures to minimize lead exposure. 

The CWS must notify the state agency or EPA if it plans to change the source or treatment of its water supply. The LCR contains additional requirements for carrying out regular monitoring, including selecting sample site locations and monitoring frequency. 

Every CWS, regardless of lead levels, must provide customers with both a CCR containing an educational statement about lead in drinking water, and a lead consumer notice that includes individual Pb tap results to people who receive water from sites that were sampled, within 30 days of learning the results. 

EPA in 2021 promulgated Lead and Copper Rule Revisions (LCRR). The LCRR maintains the 15 ppb lead AL but also establishes a 10 ppb "trigger" level. A CWS exceeding that threshold will need to take proactive steps to remove lead from the drinking water distribution system. Changes to the LSLR program include:

  • Each CWS must carry out and regularly update an LSL inventory and develop a plan to replace all LSLs

  • A CWS serving more than 10,000 customers that exceeds the AL will have to replace 3% of LSLs annually, until it no longer exceeds the AL for four consecutive six-month periods. Partial LSL replacement will not count toward that total

  • A CWS will need to replace its portion of an LSL within 45 days (or 180 days with state notification) of being notified of a customer's intent to replace their LSL portion

EPA announced on December 16, 2021, that the LCRR will go into effect immediately to support reducing lead in drinking water in the near term, while also undertaking a robust review with the aim of strengthening the rule further. The LCRR compliance date is October 16, 2024. 

EPA will continue soliciting public comment on anticipated Lead and Copper Rule Improvements (LCRI), focusing on: replacing all LSLs, compliance tap sampling, action and trigger levels and prioritizing historically underserved communities.


PFAS (per- and polyfluoroalkyl substances) are emerging chemicals of concern that have contaminated drinking water supplies across the U.S. Some of the more common applications included nonstick cookware, food wrapper coatings, stain-resistant carpets, waterproof materials, food containers and firefighting foam. Many PFAS persist in the environment and bioaccumulate, putting those exposed at risk of severe health effects. Between 18 and 80 million people in the U.S. are exposed to two priority PFAS—PFOA and PFOS—in their drinking water. A 2015 study found PFAS to be in the blood of 97% of participants in the 2012 National Health and Nutrition Examination Survey, a nationally representative sample of 5,000 Americans. Exposure to these substances above certain thresholds is linked to health impacts, including developmental effects, changes in liver, immune and thyroid function as well as increased risk of some cancers.

PFOA (perfluorooactanois acid) and PFOS (perfluorooctane sulfonic acid) are the PFAS most frequently detected in water supplies. They can cause reproductive and developmental, liver, kidney and immunological effects in laboratory animals, as well as increased cholesterol effects. An independent panel of scientists found a probable link between PFOA exposure and multiple health problems, such as high cholesterol, thyroid disease, and testicular and kidney cancer, as well as pregnancy-induced hypertension. 

EPA finalized positive regulatory determinations for PFOA and PFOS in March 2021 and is moving forward to develop national primary drinking water regulations. EPA expects to issue a proposed regulation in Fall 2022 and a final regulation in Fall 2023 after considering public comments. In addition:

  • EPA's PFAS Strategic Roadmap sets timelines for EPA to take specific actions on PFAS across environmental media between 2021 and 2024

  • EPA has included PFAS on CCL 5

  • EPA released new health advisories for GenX and PFBS and updated health advisories, with lower levels, for PFOA and PFOS. 
  • EPA is conducting hazard assessments for GenX chemicals, perfluorobutanoic acid (PFBA), perfluorodecanoic acid (PFDA), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), PFBS and PFNA

  • The National Defense Authorization Act for Fiscal Year 2020 directed EPA to include in UCMR 5 any PFAS (or class of PFAS) for which a drinking water test method has been validated and that are not already subject to a primary standard. Monitoring must be carried out by every PWS serving more than 10,000 persons, those serving between 3,300 and 10,000 subject to available funding, and only a representative sample of PWS serving fewer than 3,300. EPA proposed UCMR 5 to include nationwide drinking water monitoring for 29 PFAS under the next monitoring cycle, to take place between 2023 and 2025

  • The EPA Council on PFAS will collaborate on cross-cutting strategies, advance new science, develop coordinated policies, regulations and communications, and engage with affected states, tribes, communities and stakeholders

In the immediate absence of federal drinking water standards, some states have issued regulations for specific PFAS, although none currently regulates PFAS as a class. 


Drinking water systems are critical infrastructure, potentially vulnerable to service disruptions from extreme weather and natural disasters, cyberattacks and terrorism. EPA is the lead agency responsible for water sector security, including cybersecurity. The Public Health Security and Bioterrorism Preparedness and Response Act of 2002 added drinking water security provisions to the SDWA. Each CWS serving 3,300 or more individuals must carry out—and renew every five years— vulnerability assessments covering risk and resilience to the system from both intentional acts and natural hazards. Assessments span physical infrastructure, financial capacity and management practices. A PWS must certify its assessments and submit that certification to EPA, as well as prepare an emergency response plan based on the vulnerability assessment. Assessments are voluntary for a PWS serving fewer than 3,300, and EPA offers guidance and technical assistance to these systems.

State Programs, Enforcement and Compliance Assistance

Most states have primary enforcement responsibility over PWSs. However, if EPA learns a PWS is noncompliant with the SDWA and notifies the state, but the state fails to take appropriate action within 30 days, EPA will commence enforcement action. EPA enforces the SDWA directly in Wyoming, the District of Columbia and on most Indian reservations.

Enforcement can take the form of civil action, compliance order or injunctive relief. Civil penalties for primary standard violations take into account several factors, including the seriousness of the violation and the population at risk. Significant noncompliance refers to serious and continuous violations of most MCLs and their respective monitoring and reporting requirements, as well as violations of compliance agreements or compliance schedules. A PWS with repeated violations likely to adversely affect human health, and that is unable or unwilling to take feasible and affordable actions, may be required to assess options including consolidation or transfer of ownership.

EPA and individual states provide Small System Technical Assistance through nonprofit organizations or other means. This includes circuit-rider and multistate regional technical assistance programs, training and assistance in implementing regulations, source water protection plans, monitoring plans and water security enhancements.

Tribes and Treatment as a State

There are over 1,000 public water systems serving over one million people in Indian country where the EPA has primacy responsibilities. EPA is tasked with ensuring tribal water sources comply with SDWA requirements and conducts sanitary surveys of each PWS in all of Indian country, with exception of those on the Navajo Nation. EPA Regional offices implement the Public Water System Supervision (PWSS) program and have enforcement authority over tribal drinking water systems.

EPA may delegate to tribes primary enforcement responsibility (known as Treatment as a State, or TAS status), but tribes with primacy are not required to exercise criminal enforcement. Regulations describe the process for obtaining primacy and requesting a determination of eligibility. The application process is streamlined if a tribe has obtained TAS eligibility for similar roles, such as under the Clean Water Act or Clean Air Act. 

The Tribal Set-Aside Program offers funding for tribal water systems. As of 2021, 2% of Drinking Water SRF funding is set aside for improving the infrastructure of drinking water systems that serve tribes. The 2016 Water Infrastructure Improvements for the Nation Act (WIIN Act) expanded eligible activities, to include training and operator certification programs. EPA Regions work with Indian Health Service (IHS) and Tribes to identify, prioritize and select projects to receive funding from its share of the program funds. 

In 2021, EPA announced an action plan, Strengthening the Nation-to-Nation Relationship with Tribes to Secure a Sustainable Water Future, to address water-related challenges in Indian Country. Goals include expanding TAS programs, bolstering efforts to protect source waters for PWS in Indian country and increasing infrastructure funding and capacity development.


See drinking water system funding information on our Financing page.

Source Water Protection

The SDWA requires states to develop an EPA-approved Source Water Assessment Program (SWAP) for each PWS. These assessments inventory potential sources of contaminants and the risks they may pose for a PWS. A completed Source Water Assessment (SWA) can guide future action to protect source water supply. EPA publishes guidance and lists providers of technical assistance for developing water assessments and plans. 

Underground Injection Control Program

Over 130,000 PWSs rely on ground water supply, including nearly 38,000 CWSs. Underground Injection Control (UIC) Programs protect underground sources of drinking water (USDW). There are six classes of UIC wells. EPA has delegated primacy for all classes of wells to 35 states, shares implementation responsibility with seven states and two Indian tribes and implements the UIC program for all well classes in nine states.

Water Reuse

Nearly 340 billion gallons of water are discharged in the U.S. every day. Sources span municipal wastewater, industry process water, agriculture runoff, stormwater, and oil and gas produced water. Americans also withdraw about 322 billion gallons per day. But less than one percent of U.S. water demand is reused, despite its suitability for a variety of applications—including as a sustainable source of potable water supply.

Local governments are increasingly interested in constructing water purification facilities capable of treating effluent to potable standards to diversify drinking water sources, improve water quality and enhance resilience in the face of a changing climate. They may pursue either direct potable reuse (DPR) or indirect potable reuse (IPR):

  • DPR delivers treated wastewater effluent directly to a drinking water treatment facility.

  • IPR first diverts treated wastewater to a surface water body or groundwater aquifer, where it mixes with other raw water surfaces until it is again treated to potable standards.

EPA has not yet established federal standards specifically applicable to DPR or IPR. A number of states are developing uniform water recycling criteria, including California, Florida and Texas.

Several individual localities are piloting water purification facilities. Examples include Pure Water San Diego (IPR), Orange County, CA's Groundwater Replenishment System (GWRS) (IPR) and El Paso, TX's Advanced Water Purification Facility (DPR – in development).

EPA in 2020 issued the National Water Reuse Action Plan (National WRAP) and complementary online platform. EPA released an Update on Collaborative Progress in 2021, recognizing completion of three action items and 165 implementation milestones. In 2022, EPA announced a Water Reuse Interagency Working Group to develop and coordinate actions, tools and resources to advance water reuse across the U.S.

Organizations/Non-Government Programs

  • Association of Metropolitan Water Agencies (AMWA) An organization of the largest publicly owned water utilities in the United States, offering resources on high-priority topics, in addition to webinars on emerging trends, technology and standards within the drinking water industry. 

  • American Water Works Association (AWWA) The largest organization of water supply professionals in the world, offering educational events and training materials, a technical library and a variety of other programming and toolkits.

  • National Rural Water Association (NRWA) Non-profit organization assisting small and rural water systems through federally-funded programs, including: water circuit riders, apprenticeship program, source water protection, the SDWA compliance program and the NRWA Environmental Finance Center.

  • National Tribal Water Council (NTWC) EPA-funded organization and platform promoting education and information exchange, best management practices and awareness of tribal water quality issues.

  • National Water Research Institute (NWRI) Nonprofit that collaborates with water utilities, regulators and researchers and makes available selected reports written by panels of scientists and technical advisors.

  • Smart Water Networks (SWAN) Forum Network of water, wastewater and stormwater industry experts that provides white papers, reports, case studies, surveys and more.

  • Water Research Foundation (WRF) International water research organization that hosts an online research library and manages a database of innovative technologies.


U.S. EPA Generally

Resources for Indian Tribes

Resources on Lead and the Lead & Copper Rule (LCR)

Per- and Polyfluoroalkyl Substances (PFAS)

Water Reuse