The PFAS Private Well Gap: Federal Drinking Water Rules Stop at the Property Line
EPA's landmark 2024 PFAS drinking water rule set enforceable federal maximum contaminant levels for the first time. But those limits apply only to public water systems. The roughly 43 million Americans who rely on private wells remain outside the regulatory perimeter — a structural gap in the Safe Drinking Water Act that EPA cannot close on its own.
The gap is not an oversight or a political choice made in 2024. It is built into the text of the Safe Drinking Water Act (SDWA). The statute defines a "public water system" as a system that provides water for human consumption through pipes or constructed conveyances and regularly serves at least 25 individuals or has at least 15 service connections. Private domestic wells, by definition, serve fewer people — and Congress did not give EPA regulatory authority over them in the SDWA framework.
That distinction matters a great deal when the contaminant at issue is PFAS, a class of persistent synthetic chemicals that has now been detected in private wells across the United States. When EPA finalized its PFAS maximum contaminant levels (MCLs) in April 2024, utilities and compliance teams in public water systems received enforceable obligations. Private well users received guidance and encouragement to test voluntarily — but no federal legal protection.
What the 2024 Rule Actually Covers
EPA's final rule, published at 89 FR 32532 (April 26, 2024), established MCLs for six PFAS compounds under 40 CFR Part 141. The regulated substances are perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly called GenX), and a mixture category for combinations of PFHxS, PFNA, HFPO-DA, and perfluorobutane sulfonic acid (PFBS).
MCLs for PFOA and PFOS
The enforceable MCLs for PFOA and PFOS are 4 nanograms per liter (ng/L) each. The corresponding maximum contaminant level goals (MCLGs) for PFOA and PFOS are set at zero — reflecting EPA's determination that there is no demonstrated safe exposure threshold. The MCLs (4 ng/L) are the binding limits on covered public water systems under 40 CFR Part 141; the MCLGs (zero) are non-enforceable health targets that inform but do not replace the enforceable MCL. These are two distinct values with different legal status.
Who must comply
Community water systems and non-transient non-community water systems covered by the SDWA must comply with the MCLs. Compliance deadlines are staggered: most systems have until 2029 for monitoring and compliance. Systems serving fewer than 10,000 people have additional time for some requirements. Small water systems can also seek variances and exemptions under 42 U.S.C. § 300g-4 and § 300g-5.
The Statutory Boundary That Creates the Gap
The SDWA's definition of "public water system" in 42 U.S.C. § 300f(4) is the boundary that divides regulated and unregulated water. Systems that do not meet the 25-person or 15-connection threshold fall outside the SDWA's regulatory architecture entirely. There is no EPA rulemaking pathway under the SDWA to bring private wells under federal MCL enforcement — doing so would require a statutory amendment by Congress.
This is a classic jurisdictional gap. The gap does not mean the risk is smaller for private well users; it means the federal regulatory tool cannot reach them. EPA's authority stops at the property line.
What federal law does provide for private wells
Federal law offers some funding and research support — but not enforceable standards. The Water Infrastructure Improvements for the Nation (WIIN) Act of 2016 established a small water system technical assistance program. EPA's WaterSense and private well guidance documents are voluntary and educational. None of these create enforceable federal PFAS limits for private well users.
State authority to fill the gap
States may regulate private wells under their own drinking water and environmental laws. Some states with state primacy programs under the SDWA (42 U.S.C. § 300g-2) have addressed private wells through separate state statutes or health advisory frameworks. But state coverage is uneven. Where a state has not acted, private well users have no enforceable PFAS standard at any level of government.
Geographic and Demographic Distribution of the Risk
The private well population is not uniformly distributed. Rural communities, agricultural regions, and areas near industrial facilities with PFAS discharge history have concentrations of private well users who may face elevated PFAS exposure. EPA's own data indicates that PFAS have been detected in private wells near PFAS-manufacturing facilities, military installations that used aqueous film-forming foam (AFFF), and wastewater treatment facilities that received PFAS-laden industrial discharge.
From a legal perspective, those communities cannot invoke the federal PFAS MCLs to demand remediation from a polluter on the ground that federal drinking water standards are being violated — because the federal standard does not apply to their wells. They may have claims under CERCLA, state tort law, or state environmental statutes, but the SDWA enforcement mechanism is not available to them.
Practical Implications of the Gap
The gap has several practical legal consequences. First, public water utilities that purchase or blend groundwater from private sources face complex compliance questions about what counts as part of the regulated system. Second, real estate transactions in areas with known PFAS groundwater contamination involve disclosure and liability questions that vary by state because there is no federal baseline for private well water quality disclosure. Third, the absence of a federal standard removes an important litigation anchor for private well owners seeking relief — SDWA's citizen suit provision at 42 U.S.C. § 300j-8 does not reach private wells.
For legal and environmental compliance teams, the operational implication is straightforward. Facilities near residential areas with private wells should not treat the 2024 PFAS MCLs as the complete boundary of their PFAS liability exposure. CERCLA liability, state environmental law, and common-law tort claims remain viable independent of whether a private well is technically regulated under the SDWA. The MCL rule created enforceable obligations for public systems; it did not create a safe harbor for PFAS sources that happen to discharge near private wells.
Law Gaps exists to make these boundary conditions visible. The PFAS private well gap is a clear example of a regulatory edge where statutory jurisdiction, not agency policy preference, defines who is protected and who is not.
References & Sources
- EPA, National Primary Drinking Water Regulations for Perfluorooctanoic Acid (PFOA), Perfluorooctane Sulfonic Acid (PFOS), and Other PFAS, 89 FR 32532 (Apr. 26, 2024). Source: federalregister.gov. Used for MCL values, scope, compliance timeline, and binding nature of the final rule.
- Safe Drinking Water Act, 42 U.S.C. § 300f(4) (definition of "public water system"). Source: law.cornell.edu/uscode/text/42/300f. Used for the statutory threshold that excludes private wells from SDWA regulation.
- Safe Drinking Water Act, 42 U.S.C. §§ 300g-4, 300g-5 (variances and exemptions). Source: law.cornell.edu/uscode/text/42/300g-4. Used for the variance and exemption framework available to small public water systems.
- Safe Drinking Water Act, 42 U.S.C. § 300g-2 (primary enforcement responsibility). Source: law.cornell.edu/uscode/text/42/300g-2. Used for the state primacy framework and how state programs can supplement but not replace federal authority limits.
- Safe Drinking Water Act, 42 U.S.C. § 300j-8 (citizen civil actions). Source: law.cornell.edu/uscode/text/42/300j-8. Used for the citizen suit provision scope and its inapplicability to private wells outside the regulated system.
- EPA, PFAS Explained — Private Wells. Source: epa.gov/pfas/pfas-explained. Used as background on EPA's non-regulatory guidance posture for private well users.