The Safe Drinking Water Act of 1974 is a federal act that gives the EPA authority to place standards on contaminants found in drinking water
What is the Safe Drinking Water Act? The Safe Drinking Water Act is a federal law that authorizes the EPA to set and enforce maximum contaminant levels for public water systems serving 25 or more people. Enacted in 1974, it remains the primary federal statute regulating the quality of drinking water in the United States.
There are over 148,000 public water systems currently operating in the United States and providing water to people. In order to ensure safe water consumption, environmental regulations such as the Safe Drinking Water Act (SDWA) help keep contaminants in the public water supply at a level that is safe for humans.
History of the Safe Drinking Water Act
Summer, N.Y. / Bain News Service / Library of Congress
Throughout history, the establishment and growth of civilizations were largely dependent on their proximity to a clean water source. Without a sustainable water source, cities and towns are unable to develop the irrigation and wastewater systems required to support the needs of a growing population.
But as societies develop, many of the water sources run the risk of being contaminated with the waste and byproducts of the industries involved in keeping society afloat. Rivers often turn into dumping grounds for chemicals and human waste.
The development of the Safe Drinking Water Act of 1974 is not unlike this story.
The American Industrial Revolution: More Water, More Problems
As the American population exploded during the industrial revolution, more elaborate infrastructure was created to meet the rising demand for water among the vast population in cities. For the first time, city dwellers began to experience luxuries such as toilets, faucets, and indoor plumbing.
But the comfort and standard of living that these water systems brought also came with their own set of unforeseen drawbacks. Sewage and waste from homes began to overrun the water systems and pollute the clean water sources. By the late 1800s, waterborne diseases like Typhoid fever and cholera became rampant in metropolitan cities like New York and Philadelphia.
Consequently, in order to manage these waterborne epidemics, water treatment facilities were created to ensure clean drinking water via disinfection means such as chlorination and UV purification.
To ensure that state and local governments ensure clean water measures for the public water supply, various policies were adopted over the course of the next several decades.
But it wasn’t until 1974 that a comprehensive, unified set of federal standards were put into place.
What is the Safe Drinking Water Act of 1974?
Safe Drinking Water Act / EPA
The Safe Drinking Water Act is a federal policy that gives the Environmental Protection Agency (EPA) the jurisdiction to set minimum standards for water quality that local governments should abide by in order to ensure the safety of the public.
The EPA separates its regulation standards into two categories: Primary Standards and Secondary Standards.
National Primary Drinking Water Regulations (NPDWR) hold to the highest standard and focus on contaminants that are considered directly harmful to humans if consumed.
National Secondary Drinking Water Regulations (NSDWR) are slightly less stringent and focus on contaminants that affect the aesthetic properties of water such as color, taste, hardness, and turbidity.
There is also a category of no standards where no formal Primary or Secondary standards are applied.
Each contaminant has a certain level of concentration that the EPA deems safe. If the level of concentration rises above these standards, anyone consuming the water may be at risk and the governing body will be in violation.
National Primary Drinking Water Regulations
Contaminants that fall under the NPDWR are considered primary contaminants and have a direct impact on one’s health if consumed beyond the set standards.
The EPA further categorizes primary contaminants into the following groups:
- microorganisms
- organic chemicals
- inorganic chemicals
- disinfectants and disinfectant byproducts
- radionuclides
Microorganisms
Microorganisms are biological contaminants in water that can cause major illness if consumed. Common microorganisms are viruses such as norovirus or hepatitis A; bacteria such as cholera, typhoid, e. coli, or salmonella; or protozoa such as Cryptosporidium or Giardia.
Inorganic Chemicals
Inorganic chemicals are a class of substances that lack carbon atoms in their molecular structure. These chemicals can be naturally occurring or artificially introduced into water sources and have the potential to pose risks to human health if present above the regulated levels.
While some inorganic chemicals aren’t necessarily harmful if consumed at low levels, others such as arsenic should be avoided.
Organic Chemicals
While the term “organic” can be misleading, organic chemicals refer to a broad category of substances that do contain carbon atoms in their molecular structure. These compounds can come from various sources, including industrial processes, agricultural activities, and can also be found naturally in surface water and groundwater.
Human consumption of organic chemicals can cause various health problems depending on the concentration and duration of exposure.
Organic chemicals can be further broken down into VOCs and SOCs.
Volatile Organic Chemicals (VOCs)
VOCs are a subset of organic chemicals with properties that make them convert easily into gas at room temperature—they can come from a wide range of sources, such as solvents, fuels, and certain industrial processes.
Exposure to VOCs, either through inhalation or ingestion, can have adverse health effects on humans, including respiratory irritation, organ damage, and an increased risk of certain cancers.
Common VOCs include benzene, toluene, and formaldehyde.
Synthetic Organic Compounds (SOCs)
SOCs are man-made organic chemicals often associated with industrial activities, manufacturing processes, and the use of certain chemicals and pesticides, also known for causing major health issues if consumed.
Examples of SOCs include polychlorinated biphenyls (PCBs), dioxins, and certain pesticides like atrazine and lindane.
Disinfectants and Disinfection By-products
Disinfectants are substances used to destroy harmful microorganisms in water and are an important tool in ensuring public health by preventing the spread of waterborne diseases.
Common disinfectants used in water treatment include chlorine, chloramines, ozone, and ultraviolet (UV) light. Because disinfectants themselves can cause health problems if consumed at high concentrations, they too must adhere to EPA standards and are carefully measured when applied to water treatment processes.
The use of disinfectants can also result in the formation of unintended contaminants known as disinfection byproducts (DBPs) when disinfectants react with naturally occurring organic and inorganic matter in water. Some common DBPs include trihalomethanes (THMs), haloacetic acids (HAAs), and bromate, and are known to cause health problems when consumed at elevated levels.
Radioactive Isotopes
Radioactive isotopes are atoms that emit radiation as a result of radioactive decay.
Certain elements such as uranium, thorium, and radium can exist naturally in rocks and soil, potentially dissolving radioactive isotopes in groundwater or leaching into surface water.
Human activities can also introduce radioactive isotopes into water sources through nuclear power plants, research facilities, and radioactive waste disposal sites, releasing radioactive materials into nearby water bodies, either intentionally or through accidents and leaks.
While naturally occurring, trace levels of radioactive isotopes will be present in many water sources, prolonged exposure to high levels of radiation from radioactive isotopes can be damaging to living tissue.
View the radioactive isotopes table
PFAS (Per- and Polyfluoroalkyl Substances)
PFAS are a class of thousands of synthetic chemicals that don't break down in the environment or the human body. They've been used since the 1940s in industrial processes and consumer products — non-stick cookware, food packaging, waterproof textiles, and firefighting foam. Because they persist indefinitely, PFAS have spread into drinking water sources across the US, particularly near military bases, airports, and industrial sites where AFFF (aqueous film-forming foam) was used.
In April 2024, the EPA used its SDWA authority to finalize the first federal maximum contaminant levels (MCLs) for PFAS in drinking water. The rule set MCLs for PFOA and PFOS at 4 parts per trillion each — the lowest level reliably measurable — along with individual MCLs for PFNA, PFHxS, and HFPO-DA (GenX chemicals), and a hazard index for mixtures. Public water systems have until 2027 to comply.
The regulation has faced legal challenges, and in 2025 the EPA indicated it would reconsider the MCLs for some of the less-studied PFAS compounds while maintaining PFOA and PFOS standards. Homeowners on private wells have no federal PFAS protection under any scenario — regular testing and a reverse osmosis system (which removes PFAS effectively) remain the only reliable options.
National Secondary Drinking Water Regulations
National Secondary Drinking Water Regulations (NSDWRs) are non-mandatory water quality standards for 15 contaminants. These regulations differ from primary standards in that they are not based on health considerations but on aesthetic, cosmetic, or technical issues associated with drinking water.
Aesthetic concerns revolve around properties of water that affect consumer senses—like taste, odor, or color—while cosmetic effects relate to potential skin or tooth discoloration.
Technical effects usually involve damage to water equipment or reduced effectiveness of treatment processes for other contaminants due to the water’s characteristics.
Although these standards are not federally enforceable, the EPA recommends that all water systems serving the public meet these guidelines to enhance customer satisfaction and protect the infrastructure of water systems.
Right-to-Know Provision
The SDWA contains a right-to-know provision that states that the recipients of the public water supply must be informed should any contaminant exceed the SDWA standards at any time. Should a local utility fail to inform the public, it would be in violation of the SDWA and subject to intervention or fines.
Private Wells and the SDWA
One important aspect of the SDWA is that it only covers public water systems, but isn't enforced on private water systems such as a private well.
So what is considered a public water system?
Public supply refers to water withdrawn by water suppliers that provide water to at least 25 people or have a minimum of 15 connections.
The USGS estimates that more than 43 million people—about 15 percent of the U.S. population—rely on domestic (private) wells as their source of drinking water.
This means that those who rely on private water systems are responsible for testing and filtering their own water supply.
Bottled Water vs. Tap Water
Because bottled water is a commodity that is privately owned and sold, it isn't regulated by the EPA but by the FDA.
In fact, the FDA has slightly less stringent standards than the EPA when it comes to water contamination.
This means that there are some bottled water brands that may actually contain more contaminants than some tap water sources. In fact, some brands are known for simply bottling water at a public water utility and not from a spring or mountain source.
For households concerned about tap water quality, a reverse osmosis system at home removes a broader range of contaminants than FDA bottled water standards require — including nitrates, arsenic, and certain PFAS compounds — at a fraction of the per-gallon cost of bottled water.
The Safe Drinking Water Act sets minimum standards for public water systems, but it doesn't protect every household equally — private wells, bottled water, and emerging contaminants like PFAS operate in gaps the law hasn't fully closed. Check your utility's Consumer Confidence Report to see what contaminants were detected in your water last year. If you rely on a private well or want protection beyond SDWA minimums, start with a water quality test and match the results to the right home filtration system.
Safe Drinking Water Act: FAQs
What are the main provisions of the Safe Drinking Water Act?
The SDWA's core provisions are: (1) it authorizes the EPA to set enforceable National Primary Drinking Water Regulations — maximum contaminant levels (MCLs) for contaminants that threaten health; (2) it establishes non-enforceable National Secondary Regulations for aesthetic issues like taste, odor, and color; and (3) it includes a public "right-to-know" provision requiring utilities to notify customers when standards are violated and to publish an annual Consumer Confidence Report. It applies only to public water systems serving 25+ people or 15+ connections.
What is the difference between the Clean Water Act and the Safe Drinking Water Act?
They regulate different things. The Safe Drinking Water Act governs the quality of treated drinking water delivered to your tap from public water systems. The Clean Water Act (1972) instead regulates pollutant discharges into surface waters — rivers, lakes, and streams — and sets water-quality standards for those bodies of water. In short: the Clean Water Act protects the source water and the environment; the Safe Drinking Water Act protects the water you actually drink.
Does the Safe Drinking Water Act cover private wells and bottled water?
No. The SDWA only covers public water systems. Private wells (about 43 million Americans) are not regulated under it — owners are responsible for their own testing and treatment. Bottled water is regulated by the FDA, not the EPA, under generally comparable but slightly less stringent standards.
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