PFAS Drinking Water Rules: What’s Final, What’s Proposed, and What Your System Should Do Now
The 2024 final rule (still the law today)
In April 2024, EPA finalized the first-ever National Primary Drinking Water Regulation for PFAS under the Safe Drinking Water Act, covering six compounds:
| PFAS | MCL | Status (Oct 2026) |
|---|---|---|
| PFOA (perfluorooctanoic acid) | 4.0 ppt | FINAL — stays |
| PFOS (perfluorooctane sulfonic acid) | 4.0 ppt | FINAL — stays |
| PFHxS | 10 ppt | PROPOSED for rescission |
| PFNA | 10 ppt | PROPOSED for rescission |
| HFPO-DA (GenX chemicals) | 10 ppt | PROPOSED for rescission |
| Mixture of PFHxS + PFNA + HFPO-DA + PFBS | Hazard Index 1.0 (unitless) | PROPOSED for rescission |
Under the 2024 rule, public water systems must complete initial monitoring by 2027 and comply with MCLs (running annual average) beginning with the 2027–2029 window. Those monitoring and reporting deadlines remain in force — EPA reaffirmed this in its May 2026 PFAS strategy.
The May 2026 proposals: two separate actions
On May 18–20, 2026, EPA issued two proposed rules. Proposals signal direction; they do not change legal obligations until finalized.
Proposal 1 — PFOA & PFOS: keep the limits, extend the deadline
EPA proposes to retain and defend the 4.0 ppt MCLs for PFOA and PFOS while allowing eligible systems to extend the MCL compliance deadline from April 26, 2029 to April 26, 2031. To qualify, a system would need to show compelling reasons it cannot meet 2029 and that the extension poses no unreasonable health risk. EPA cited implementation challenges for small, rural, and disadvantaged communities.
Proposal 2 — rescind the other four
EPA proposes to rescind the MCLs (and MCLGs and regulatory determinations) for PFHxS, PFNA, HFPO-DA, and the Hazard Index mixture, arguing the 2024 rulemaking used a flawed procedure for these compounds — and commits to re-evaluating them through the proper statutory process with fuller public comment. If finalized, these four would return to the regulatory queue rather than disappear forever.
August 2026: EPA withdrew source-water PFAS guidance
In an August 11, 2026 memo (reported publicly in mid-September), EPA’s Office of Water withdrew guidance directing states to use Clean Water Act authorities — NPDES permits and pretreatment — to keep PFAS out of source water. The Clean Water Act’s statutory obligations didn’t change, but the federal roadmap for stopping PFAS before it reaches intakes is gone. Practically, this shifts more of the burden — and cost — to treatment at the drinking water plant (granular activated carbon, ion exchange, or reverse osmosis), paid for by water ratepayers rather than dischargers.
Don’t forget the states
Several states set PFAS standards before EPA and some are stricter than the federal rule. State primacy agencies can keep enforcing their own limits regardless of what EPA finalizes. Your compliance plan must satisfy the stricter of the two — check your state’s current PFAS requirements separately.
What your system should do now — checklist
- Keep your initial monitoring on schedule (2024 rule: complete by 2027) using EPA Methods 533/1633 at a certified lab.
- Track detections against both the 2024 MCLs and any state limits — report as required; monitoring/reporting deadlines are unchanged.
- If PFOA/PFOS exceed 4 ppt, start treatment evaluation now (GAC, anion exchange, RO) — don’t wait for the 2031 extension question to resolve.
- Document everything: the extension application (if proposed as final) will require recent sampling data and certifications.
- Follow the two 2026 dockets to finalization; set a calendar reminder to re-check quarterly.
- Review source-water protection options with your state, since federal CWA guidance was withdrawn.
- Prepare consumer communication language — PFAS questions from the public are only increasing.
Frequently asked questions
Are PFAS still regulated in drinking water?
Yes. The 2024 NPDWR is final and enforceable. The 2026 actions are proposals — they change nothing until finalized.
If the four MCLs are rescinded, can we ignore PFHxS, PFNA, and GenX?
No. They’d return to re-evaluation, many states regulate them independently, and they remain reportable where state rules apply. Keep monitoring.
Does the 2031 extension apply automatically?
As proposed, no — systems would have to apply and demonstrate compelling need. And it’s not final yet.
What treatment removes PFAS?
The demonstrated technologies are granular activated carbon (GAC), anion exchange resin, and reverse osmosis/nanofiltration. Selection depends on which PFAS, concentrations, water chemistry, and residuals handling — pilot testing is the norm, not the exception.
Related free tools
- Drinking Water Compliance Center — PFAS limits, methods, and citations in one lookup
- Free Compliance Self-Check Checklist (PDF) — includes a PFAS status-check section
- LCRI Explained — the other big rule with a 2027 compliance date
Prepared by Practical Notes Lab (practicalnoteslab.com) for education and preliminary planning. Regulatory status changes quickly — verify all requirements, dates, and state-specific provisions with your primacy agency and the Federal Register. Sources consulted: EPA 2024 PFAS NPDWR; EPA May 2026 proposed rules (Docket EPA-HQ-OW-2025-1742); EPA May 2026 PFAS strategy; legal analyses of the proposals. Last updated October 1, 2026.