PFAS in drinking water: limits, deadlines, and treatment.
PFAS (per- and polyfluoroalkyl substances), often called 'forever chemicals,' are a large family of synthetic compounds found in many water supplies. In 2024 the EPA set the first national limits — 4.0 parts per trillion for PFOA and for PFOS. Public water systems must complete initial monitoring by 2027; the compliance deadline is 2029, which the EPA has proposed extending to 2031.
Where the PFAS drinking water rule stands
The PFAS rule is being actively reconsidered. Here is what is final and what is still proposed — always confirm against the latest EPA and state guidance before you act.
The limits (final)
The 2024 rule set enforceable MCLs of 4.0 parts per trillion (ppt) each for PFOA and PFOS. The EPA has said it will keep these two limits.
The timeline
Systems have until 2027 to finish initial monitoring. The MCL compliance deadline is 2029 — the EPA has proposed giving systems an option to extend to 2031.
The four others (proposed rescission)
Limits for PFHxS, PFNA, GenX (HFPO-DA), and the Hazard Index mixture were part of the 2024 rule, but as of mid-2026 the EPA has proposed to rescind them. Their status is not final.
How utilities remove PFAS
Granular activated carbon (GAC)
The most widely used PFAS treatment. Water passes through carbon beds that adsorb PFAS; media is replaced on a schedule driven by breakthrough monitoring.
Ion exchange (IX)
PFAS-selective resins capture PFAS efficiently and can handle shorter-chain compounds well. Often used where a compact footprint or high removal is needed.
Reverse osmosis / high-pressure membranes
Membranes physically reject PFAS along with many other contaminants. Highly effective, but generate a concentrate stream that must be managed and use more energy.
The hard part isn’t the chemistry — it’s the tracking.
PFAS compliance means a monitoring schedule, running-average calculations, exceedance triggers, and public notification — on a timeline that keeps shifting. Small systems rarely have staff to babysit it.
1water is building PFAS sampling-schedule and compliance-tracking tools so small systems can stay ahead of the deadlines without an enterprise contract. Tell us your state →
PFAS in drinking water — common questions
- U.S. EPA — PFAS National Primary Drinking Water Regulation (final rule, April 2024).
- U.S. EPA — Proposed PFOA and PFOS Compliance Extension Rule and Proposed PFAS Rescission Rule (2026); comment period open as of mid-2026.
Keep reading
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How to become a certified water operator — exam and experience requirements, certification classes, reciprocity, and renewal.
Sanitary survey: the 8 elements and how to prepare
The eight elements a sanitary survey evaluates, how often surveys happen, and how to prepare for yours.
Compliance shouldn't wait for a crisis.
1water helps small and mid-size water systems stay ahead of PFAS, lead, coliform, and CCR requirements — self-serve, and priced for the small end.