Drinking water in the United States is regulated by more than one agency, and which one applies depends on where your water comes from. The Environmental Protection Agency (EPA) sets and enforces the national standards for tap water delivered by public water systems under the Safe Drinking Water Act. Most states run the day-to-day enforcement of those standards under EPA oversight. The Food and Drug Administration regulates bottled water as a packaged food. And private wells serving fewer than 25 people are not federally regulated at all, leaving roughly 23 million households responsible for their own testing.
The EPA Sets the National Rules for Tap Water
The Safe Drinking Water Act, first passed in 1974 and amended several times since, gives the EPA authority to set minimum standards for tap water and requires public water system operators to meet them.1U.S. Environmental Protection Agency. Summary of the Safe Drinking Water Act The law covers water “actually or potentially designed for drinking use,” whether it comes from surface sources like lakes and rivers or from underground aquifers. The EPA’s Office of Ground Water and Drinking Water, working with states, tribes, and other partners, oversees more than 148,000 public water systems nationwide.2U.S. Environmental Protection Agency. Information about Public Water Systems
A “public water system” under the SDWA means any system that provides water for human consumption through pipes or other constructed conveyances and has at least 15 service connections or regularly serves at least 25 people.3Office of the Law Revision Counsel. 42 U.S. Code 300f – Definitions That definition sweeps in municipal utilities, some private water companies, and systems serving places like schools and office buildings. Anything smaller falls outside the SDWA.
How EPA Standards Work
The EPA sets legally enforceable limits called Maximum Contaminant Levels (MCLs) for substances that may pose health risks. The agency currently regulates over 90 contaminants, ranging from bacteria and viruses to heavy metals, pesticides, and industrial chemicals.4Environmental Protection Agency. Drinking Water Regulations Each MCL reflects two considerations: the level that protects human health and what water systems can realistically achieve using available treatment technology.
Behind each MCL sits a Maximum Contaminant Level Goal (MCLG), a non-enforceable health target set at the level where no known health effects would occur. MCLGs for cancer-causing contaminants are often set at zero. The enforceable MCL is then set as close to the MCLG as feasible given current technology and cost. The EPA also sets testing schedules and approved methods that water systems must follow to demonstrate compliance.
Two recent rule updates show how these numbers change over time. In April 2024, the EPA finalized the first national drinking water standards for per- and polyfluoroalkyl substances (PFAS), setting MCLs of 4.0 parts per trillion for both PFOA and PFOS, with MCLGs of zero for each.5U.S. Environmental Protection Agency. Per- and Polyfluoroalkyl Substances (PFAS) As of May 2025, the EPA confirmed it will keep those standards in place. In October 2024, the agency finalized the Lead and Copper Rule Improvements (LCRI), which lowers the lead action level from 15 to 10 parts per billion and requires water systems to replace all lead service lines under their control within 10 years of the compliance date.6Federal Register. National Primary Drinking Water Regulations for Lead and Copper Improvements LCRI Systems must comply with the new LCRI requirements starting three years after the rule’s promulgation.
States Handle Most of the Enforcement
The EPA writes the rules, but most day-to-day enforcement happens at the state level. The SDWA allows the EPA to delegate primary enforcement responsibility, known as “primacy,” to states and tribal governments that meet certain requirements.7U.S. Environmental Protection Agency. Primacy Enforcement Responsibility for Public Water Systems Nearly every state has taken on this role. To qualify, a state must adopt contaminant regulations that are no less stringent than the EPA’s National Primary Drinking Water Regulations.
State environmental or health agencies then oversee public water systems within their borders, conducting inspections, providing technical assistance, and enforcing compliance. Many states go further than federal minimums, setting stricter limits for certain contaminants or regulating substances the EPA has not yet addressed. So the standards your water system actually must meet depend partly on where you live. In places that have not obtained primacy (currently only Wyoming and the District of Columbia among states and territories), the EPA handles enforcement directly.
Bottled Water Is Regulated by the FDA
Bottled water sits in a separate lane. Because it is classified as a packaged food product, bottled water is regulated by the Food and Drug Administration rather than the EPA.8U.S. Food and Drug Administration. FDA Regulates the Safety of Bottled Water Beverages Including Flavored Water and Nutrient-Added Water The SDWA does not apply to bottled water at all.
Federal law requires the FDA to set bottled water contaminant limits that are no less stringent than the EPA’s MCLs for tap water.9GovInfo. 21 U.S. Code 349 – Standards for Bottled Drinking Water On paper, then, the contaminant limits are comparable. In practice, the two systems differ in important ways. Public water systems must test frequently and report results to regulators and the public. The FDA does not require the same testing frequency or public disclosure from bottled water companies. Bottled water sold and distributed within a single state may also fall outside federal FDA jurisdiction entirely, since the FDA’s authority generally extends to products in interstate commerce.
Private Wells Are Not Federally Regulated
This is the gap that surprises many people. The Safe Drinking Water Act does not regulate private wells serving fewer than 25 individuals.10U.S. Environmental Protection Agency. Overview of the Safe Drinking Water Act The EPA estimates that more than 23 million households, representing over 43 million people (roughly 15 percent of the U.S. population), rely on private wells for drinking water.11U.S. Environmental Protection Agency. Private Drinking Water Wells
If you’re on a private well, no federal agency is testing your water or requiring your well to meet any contaminant standard. The responsibility falls on you as the property owner. Some states and local health departments offer limited testing, often just for bacteria, but testing for minerals, chemicals, or other contaminants typically requires hiring a private laboratory. The EPA recommends well owners test at least annually for coliform bacteria, nitrates, total dissolved solids, and pH, and more often if you notice changes in taste, odor, or color.
How to See Your Own Water Quality Results
If your home is on a public system, you have a right to see what’s in your water. Every community water system must send its customers an annual Consumer Confidence Report (CCR), sometimes called a water quality report. The CCR Rule requires these reports to include the source of your drinking water, all detected contaminants subject to mandatory monitoring, and whether any results exceeded an MCL or triggered another violation.12U.S. Environmental Protection Agency. Consumer Confidence Reports – Required Information Reports must be delivered by July 1 each year and cover the previous calendar year’s monitoring data.
If you haven’t seen yours, contact your water utility directly or check the EPA’s online CCR search tool. If your water comes from a system that isn’t classified as a community system, such as a seasonal campground, the CCR requirement may not apply, but the system must still meet the same contaminant standards.
For concerns about taste, odor, or appearance, start with your local utility, which is required to investigate. Problems that don’t get resolved can be taken to your state’s primacy agency. The EPA’s Safe Drinking Water Hotline (800-426-4791) can point you toward the right office if you’re not sure who to call.