EPA's PFAS Drinking Water Rule Explained: Limits, Deadlines, and What Has Changed

In April 2024, EPA set the first enforceable national limits for PFAS (“forever chemicals”) in public drinking water. The rule limits PFOA and PFOS to 4.0 parts per trillion (ppt) each and sets limits for four other PFAS. Since then, EPA has changed course on part of it. In May 2026 it proposed two changes. One would give water systems the option to ask for two more years, until 2031, to meet the PFOA and PFOS limits. The other would repeal the limits for the other four PFAS. As of October 2026, both are still proposals. Neither has been finalized, and the 2024 rule is still the regulation on the books.

Here is what the rule requires, what EPA has proposed to change, and what it means for your tap water.

What the April 2024 rule set

EPA announced the PFAS National Primary Drinking Water Regulation on April 10, 2024, and published it in the Federal Register on April 26, 2024. It covers six PFAS:

PFAS	Enforceable limit (MCL)	Health goal (MCLG)
PFOA	4.0 ppt	Zero
PFOS	4.0 ppt	Zero
PFHxS	10 ppt	10 ppt
PFNA	10 ppt	10 ppt
HFPO-DA (“GenX”)	10 ppt	10 ppt
Mixture of PFHxS, PFNA, HFPO-DA and PFBS	Hazard Index of 1	Hazard Index of 1

A few terms explain the table:

MCL (Maximum Contaminant Level) is the legal limit a water system must meet. Compliance is based on a running annual average, not a single sample.
MCLG (Maximum Contaminant Level Goal) is a non-enforceable health goal. EPA set it at zero for PFOA and PFOS, which means the agency did not identify a level of exposure without risk.
Parts per trillion (ppt) is an extremely small concentration. One ppt is one part PFAS per trillion parts water.

How the Hazard Index works

The Hazard Index is a way to limit a mixture of PFAS that may add up to harm, even when each one is below its own limit. For each sample, a utility divides the level of each compound by a health-based number, then adds the results:

PFHxS, PFNA and HFPO-DA are each divided by 10 ppt.
PFBS is divided by 2,000 ppt.

If the total is above 1, the mixture exceeds the limit. EPA’s guidance notes that a Hazard Index violation requires two or more of these PFAS to be present at measurable levels. PFBS has no limit of its own, so PFBS alone cannot cause a violation.

The original deadlines

The 2024 rule applies to community water systems and to non-transient non-community systems (such as schools or factories with their own water supply). It set two key dates:

By April 26, 2027: complete initial PFAS monitoring, then begin ongoing compliance monitoring and report PFAS results to customers.
By April 26, 2029: meet the limits. Starting then, a system above a limit is in violation and must notify the public.

The five-year gap was meant to give utilities time to install treatment, such as granular activated carbon, ion exchange or reverse osmosis.

What changed in 2025 and 2026

May 14, 2025: EPA announces a new direction

EPA said it would keep the 4.0 ppt limits for PFOA and PFOS. It also said it planned to:

Extend the PFOA and PFOS compliance deadline from 2029 to 2031.
Rescind the regulations for PFHxS, PFNA, HFPO-DA and the Hazard Index mixture, and reconsider whether to regulate them.
Create a federal exemption framework and add outreach to utilities, especially small and rural systems, that need capital upgrades.

That announcement did not change the rule by itself. Changing a drinking water regulation requires a new rulemaking.

The court case

Water utility trade groups challenged the 2024 rule in the U.S. Court of Appeals for the D.C. Circuit (AWWA v. EPA, No. 24-1188). In September 2025, EPA asked the court to throw out the four non-PFOA/PFOS limits, citing procedural errors in how they were adopted. The court denied that request in January 2026. It said the merits were not clear enough for that kind of summary action. In March 2026 it also denied EPA’s request to separate those claims and put them on hold. EPA has said it will continue to defend the PFOA and PFOS limits.

May 18, 2026: two proposed rules

EPA then proposed two separate rules, published in the Federal Register on May 20, 2026:

More time for PFOA and PFOS. The 4.0 ppt limits stay. EPA describes this as an exemption: eligible water systems could receive up to two more years, to April 2031, instead of the April 2029 deadline. It would apply in states, territories and Tribes that have not taken over enforcement (primacy) of the PFOA and PFOS limits, and it would not be automatic. Systems with an exemption would have to tell customers about it each year, take short-term steps if PFOA or PFOS is at or above 12 ppt, and monitor at the most frequent schedule if levels are at or above 4.0 ppt.
Repeal of four limits. EPA proposed to rescind its decisions to regulate PFHxS, PFNA, HFPO-DA and the Hazard Index mixture, and to remove those limits. EPA said the reason is procedural: in 2024 it made the decision to regulate and set the standards at the same time, when the Safe Drinking Water Act requires those steps to happen in order. EPA stated the proposal is not based on new findings about health effects, and it has said it may regulate these chemicals again later through a new process.

The comment period closed July 20, 2026, after a public hearing on July 7.

Where things stand as of October 2026

The 2024 rule remains the regulation in effect. Neither 2026 proposal has been finalized, based on EPA’s PFAS rule page and the Federal Register as of early October 2026.
The PFOA and PFOS limits of 4.0 ppt are not proposed to change. Only the deadline may move, and only for systems that apply.
The limits for PFHxS, PFNA, GenX and the Hazard Index could be removed if EPA finalizes the rescission. That could also face legal challenge.
The 2027 monitoring deadline stands. EPA said in May 2026 that all monitoring and reporting deadlines under the April 2024 rule remain in force. We could not confirm how monitoring for the four other PFAS would change if the rescission is finalized.

We will update this post when EPA issues final rules.

State limits still apply

Federal limits are a floor. Several states have set their own PFAS limits or guidance levels, and those stay in force no matter what happens federally. Check your state drinking water program or your state page, such as /states/, for local rules.

What this means for your tap water

The rule changes timelines on paper. It does not change what is in your water today. A few practical steps:

1. Check whether your utility has tested for PFAS. Many utilities already sampled for PFAS under EPA’s fifth Unregulated Contaminant Monitoring Rule (UCMR 5). Your annual water quality report, or Consumer Confidence Report, may include results. Our guide on how to read your water quality report explains where to look. You can also find your water system to see its grade and EPA compliance record.

2. Compare results to 4 ppt, not just “no violation.” Until the compliance date, a utility can have PFOA above 4 ppt without being in violation. A clean violation record does not mean low PFAS levels.

3. If levels are a concern, use a certified filter. Look for certification to NSF/ANSI 53 (carbon and other filters) or NSF/ANSI 58 (reverse osmosis) with a specific PFOA and PFOS reduction claim. NSF folded its older P473 PFAS protocol into those two standards, and current editions also include a “Total PFAS” claim. Read our NSF certifications guide and our roundup of the best water filters for PFAS removal. Before buying, confirm the exact model in the certifier’s online listing.

4. Do not boil water to remove PFAS. EPA says heating or boiling water does not remove PFOA or PFOS.

5. Talk to a doctor if you have specific health concerns. This matters most during pregnancy, for infants on formula, or if you have a known exposure. EPA says lowering PFAS exposure is expected to prevent certain cancers and liver and heart effects in adults, and immune and developmental effects in infants and children.

Bottom line

The national 4.0 ppt limits for PFOA and PFOS still stand. The open questions are how long utilities have to meet them and whether the other four limits survive. As of October 2026, EPA has proposed extending the PFOA and PFOS deadline to 2031 for systems that apply and repealing the other four limits. Neither change is final. If you want to know your exposure now, check your utility’s PFAS results. If they are above 4 ppt, a filter certified for PFOA and PFOS reduction is a practical step you can take today.