PFAS in well water: which rules apply, how to test, and what your result means

PFAS are the hardest well contaminant to handle on your own. You can't taste, see or smell them, and the yearly tests CDC recommends (bacteria, nitrate, dissolved solids, pH) don't include them. Federal limits for public water were set in 2024 and proposed for change in 2026. And EPA, your state and the state next door judge the same result by different numbers. Here is what is in force as of November 4, 2026, and how to test, read and treat.

What PFAS are and why they last

Per- and polyfluoroalkyl substances are manufactured chemicals that, in EPA's words, "have been used in industry and consumer products since the 1940s." The National Institute of Environmental Health Sciences counts "nearly 15,000 synthetic chemicals" in the group, citing EPA's CompTox database. EPA calls PFOA and PFOS "two of the most widely used and studied chemicals in the PFAS group." Wisconsin's health department notes they have been phased out of commercial products but "are still found in the environment from historical uses and in some firefighting foams."

The "forever chemicals" nickname comes from their structure. NIEHS explains that PFAS molecules "have a chain of linked carbon and fluorine atoms. Because the carbon-fluorine bond is one of the strongest, these chemicals do not degrade easily in the environment." It adds that people "may take in more of the chemicals than they excrete," so PFAS build up in the body. For a well owner, that means use from decades ago can still matter today. And a clean result on one compound doesn't rule out others, because labs measure a fixed list.

The rules: what is in force and what is only proposed

This changed in 2026. Here is what EPA's own pages say, with their dates.

The April 2024 rule (still the rule on the books)

On April 10, 2024, EPA announced the final National Primary Drinking Water Regulation for six PFAS. EPA's PFAS rule page (last updated May 18, 2026) lists these enforceable Maximum Contaminant Levels (MCLs) and non-enforceable health goals (MCLGs):

EPA says compliance "is determined by running annual averages at the sampling point." The original schedule gave public systems until 2027 for initial monitoring and until April 26, 2029 to meet the limits. That 2029 date is no longer certain for PFOA and PFOS: EPA's May 2026 proposal would give systems that request and are granted a federal exemption until April 26, 2031 (proposed, not final; details below).

The Hazard Index is the one number you can't read straight off a lab report. EPA's Hazard Index fact sheet (April 2024) builds it as a sum of fractions: GenX ÷ 10 ppt, plus PFBS ÷ 2,000 ppt, plus PFNA ÷ 10 ppt, plus PFHxS ÷ 10 ppt. A running annual average above 1 is a violation. EPA's reasoning: "low levels of multiple PFAS that individually would not likely result in adverse health effects may pose health concerns when combined in a mixture."

The May 18, 2026 proposals (not final)

EPA's rule page now opens: "On May 18, 2026, EPA announced two proposed rules related to PFAS in drinking water for public comment." One "upholds the NPDWR for PFOA and PFOS" while giving systems "an option... to request two additional years - to 2031 - to comply." The other would "rescind drinking water regulations for PFHxS, PFNA, HFPO-DA (commonly known as GenX), and the Hazard Index mixture of these three PFAS plus PFBS." Both appeared in the Federal Register on May 20, 2026 (rescission, 91 FR 29413; extension, 91 FR 29425).

• EPA's proposed rescission page (last updated October 8, 2026): "The comment period for the proposed rule closed on July 20, 2026." EPA says the proposal corrects "the unlawful procedure under which regulations for these PFAS were promulgated," and that after rescinding it will evaluate PFAS for future regulation, where "it is possible that the result could be more stringent requirements."
• EPA's PFOA and PFOS extension page (also October 8, 2026): the proposal "does not change the PFOA and PFOS MCLs... which remain 4.0 parts per trillion (ppt) each." Systems granted an exemption (to April 2031) with a result "at or above 12 ppt would be required to implement short-term mitigation actions."

Has anything become final? No. Both EPA pages still call the rules "proposed," and a Federal Register search on November 4, 2026 found no final rule on either. Today the 2024 rule, all six limits included, is the regulation. A final rule could come at any time, so check EPA's pages.

None of it applies to your well. EPA's PFAS in Private Wells page (updated June 9, 2026) says the agency "does not regulate or provide recommended standards for private wells." Several states use the federal numbers, or their own, to judge a private-well result. The table under "Reading your result" compares them.

How PFAS reach a well

Agencies list a similar set of sources. These are sources, not reasons to test; testing advice follows.

• Firefighting foam. EPA says these foams "are used in training and emergency response events at airports, shipyards, military bases, firefighting training facilities, chemical plants, and refineries." New Jersey's health department names "past use of aqueous firefighting foams, industrial release, and discharge from sewage treatment plants."
• Industry and waste sites. EPA lists facilities that make or use PFAS (chrome plating, electronics, certain textile and paper makers) and "landfills, disposal sites, and hazardous waste sites."
• Biosolids and land application. EPA lists biosolids used on farmland, which "can affect ground and surface water." New York's DEC lists "land application practices."
• Wastewater and septic. The same New York fact sheet (May 2023) names "wastewater treatment plants, consumer products, and septic systems."

A 2024 USGS groundwater study analyzed 1,238 groundwater samples and modeled how "urban development and well depth can impact PFAS occurrence." It estimated that 71 to 95 million people in the Lower 48 "may rely on groundwater that contains detectable concentrations" of PFAS. Michigan, Florida, North Carolina, Pennsylvania, New York and Ohio had the largest private-well populations relying on potentially contaminated groundwater, and in Connecticut the figure was "67 to 87% of the people who rely on groundwater from private wells." The USGS adds that the model is meant for "state, regional and national scales rather than at individual household levels," and that "testing is the only way to confirm."

Tap water tells a similar story. A 2023 USGS study (Smalling and others, Environment International) sampled taps at 716 locations, 269 of them private wells, between 2016 and 2021, testing for 32 PFAS. It found that "PFAS profiles and estimated median cumulative concentrations were similar among private wells and public-supply tapwater," and estimated "at least one PFAS could be detected in about 45% of US drinking-water samples." The USGS put the chance of finding none at "about 75% in rural areas and around 25% in urban areas." Rural odds are lower, not zero.

Who should test: what the states actually say

State advice ranges from "test only near known contamination" to New Jersey's requirement at a home sale.

One Minnesota line matters for families: "Prepare infant formula with filtered tap water or bottled water if your private well has not been tested for PFAS." If you're pregnant, nursing or feeding a baby, ask your doctor or health department what fits your situation.

Free testing programs

New York's Private Well PFAS Testing and Mitigation Rebate Pilot. The pilot page (revised October 2026) "offers limited, free private well testing and rebates for PFAS water treatment in six counties": Dutchess, Orange, Putnam, Suffolk, Ulster and Westchester. Per the page:

• Owners and renters with a private well there can apply for testing (renters need a Property Owner Acknowledgment form), as can businesses that are transient non-community water systems. "Only property owners can apply for a rebate." Not eligible: homes on public water, homes that already have a whole-house PFAS system installed outside the program, homes previously offered alternate water through a remediation program, and agriculture-only wells.
• Testing uses "EPA Method 537.1 version 2." Rebates require PFOA or PFOS at or above New York's standard of "10 nanograms per liter (ng/L) or 10 parts per trillion (ppt)": up to $5,000 for a whole-house carbon or ion exchange system, up to $1,000 for point-of-use (only where whole-house isn't feasible), up to $10,000 to connect to public water. In-home systems need a post-treatment test showing PFOA and PFOS below 10 ng/L.
• Funds are limited, and the program "may pause."

Our New York lab list shows the state's table of labs for those tests.

Wisconsin's PFAS Private Well Testing program (WisPPWT). The DNR page says eligible owners and users get "a home sampling kit at no cost." A well is "conditionally eligible" if it "has not been previously sampled by the DNR" and isn't in a Community Grants Sampling Program. Wells already on DNR or responsible-party bottled water for PFAS, homes on public water, wells reconstructed after known contamination, and transient non-community systems are not eligible. Expect "approximately 3-4 months" from application to results. Wells above the state health advisories may qualify for temporary water and a Well Compensation Grant. See our Wisconsin lab list.

Minnesota lists no general free program. To test on your own, MDH points to its accredited-lab search (category "Emerging Contaminant," with "Accepts samples from private home owners" checked). Our Minnesota list includes only labs that accept private-well samples.

Testing: methods, compounds, reporting limits and cost

Ask for an EPA drinking-water method

EPA's drinking water methods page says Method 537.1 (2018, editorial update to version 2.0 in 2020) can "quantitate 18 PFAS in drinking water, including HFPO-DA." EPA's method comparison table says Method 533 "focuses on 'short chain'" PFAS and that "using both methods, a total of 29 unique PFAS can be effectively measured in drinking water."

Either method covers every PFAS in the 2024 rule. Ask which compounds the lab reports.

Reporting limits: how low the lab can see

PFAS limits are so low that the lab's reporting limit decides what your report can tell you. New York's Understanding Your Lab Report defines the terms:

• RL, reporting limit: "The level that the laboratory equipment can reliably detect."
• MDL, method detection limit: "The lowest level that the laboratory equipment could detect."
• ND: below what the equipment could measure.
• J: detected "at a level greater than the method detection limit but less than the reporting limit."
• B: "detected in a blank sample and the sample result may be biased high."

That guide's example report has a reporting limit of 1.8 ng/L. EPA's minimum reporting level for PFOA and PFOS in national public-system monitoring (UCMR 5) was 0.004 µg/L, or 4 ng/L. Units: 1 ng/L = 1 ppt, and 1 µg/L = 1,000 ng/L. Maine CDC says "ng/L" and "ppt" "refer to the same concentration of PFAS in water." Ask the lab whether its PFOA and PFOS reporting limits are at or below 4.0 ng/L. If they aren't, "not detected" can't tell you whether your water is under the federal number.

What it costs

• The Wisconsin State Laboratory of Hygiene lists EPA 537.1 for private well water, 18 compounds, at $680 total: $380 for the sample plus $300 for a field reagent blank "if analyzed." Its 40-compound EPA 1633A water test is $450 (prices effective November 1, 2025).
• New York's DEC says "Tests may range from $300-$600," done by "a small number of certified laboratories."
• New Jersey's health department puts the average cost of its whole home-sale panel, which includes PFAS, at $1,250 (fact sheet updated January 2023).

Why sampling is fussier for PFAS

At parts per trillion, a trace of contamination during sampling can show up in the result. That's what the field reagent blank is for. The Wisconsin lab describes it as "a bottle of PFAS-free water that travels from the lab to the sampling site, is poured into an empty bottle, and travels back to the lab with the sample." It's analyzed only if PFAS turn up in your sample, and it's optional for homeowners. Wisconsin's kit instructions show the care involved: use "an unfiltered or untreated faucet," run it about a minute, fill two bottles "to the shoulder" without overfilling, pack them on ice, and don't ship on Friday or Saturday. Follow your own lab's instructions first; New York's DEC notes some labs will sample for a fee. General steps are in our guide to testing well water, and the PFAS lab finder lists labs that state certification lists name for PFAS.

Reading your result

Check the units, then compare each compound with the benchmark your state uses. Every value below is from the page named, on the date shown. None is written as a limit a private well must meet. New York's DEC says the state "does not regulate PFAS in private wells"; Maine and Vermont apply their standards to public water; Wisconsin's values are health advisories; and MDH uses its values "to evaluate potential human health risks from exposures to chemicals in groundwater."

Minnesota publishes in µg/L; the figures above are multiplied by 1,000. Its PFOA cancer value of 0.0079 ng/L is far below the 1.8 ng/L reporting limit on New York's example report, so a test like that can't show whether water is under it. MDH's private-well page (October 2024) said something similar about EPA's earlier advisories: "Currently, laboratories cannot test water down to the level of the new EPA health-based guidance values."

Vermont adds: "Some PFAS (like PFOA, PFOS, PFNA, and PFDA) can cause health effects at levels below the MCLs. Consider treating your water if PFAS are detected in your water below the MCLs." EPA: water above the federal standard "does not necessarily mean that adverse health effects will occur," because risk depends on the level, how long you're exposed, and individual factors. You can enter your numbers in our results checker.

Worked example: a typical low-level report

Take the example results in New York's lab-report guide: PFOA 1.8 ng/L, PFOS 2.7, PFBS 2.6, PFHxS 0.86 (J), PFHxA 1.0 (J), with PFNA and PFDA not detected.

1. EPA. PFOA and PFOS are both under 4.0. Hazard Index by EPA's formula: 2.6 ÷ 2,000 + 0.86 ÷ 10 ≈ 0.09, well under 1 even counting the J-flagged PFHxS. GenX isn't on New York's example report, so it's left out of the sum.
2. New York. Both under 10, so no rebate.
3. Maine. Sum of the six: 1.8 + 2.7 + 0.86 = 5.4 ng/L, under 20.
4. Minnesota. PFOS at 2.7 is above the 2.3 ng/L non-cancer value, and PFOA is above both Minnesota PFOA values.
5. Vermont. Under every MCL, but PFAS were detected, which is when Vermont says to "consider treating."

Same water, different verdicts. Now change it to PFOS 6.0 and PFOA 3.0: PFOS is over EPA's 4.0 and Wisconsin's advisory, but under New York's 10, so New York's rebate wouldn't apply. If you get a high result, New Jersey's health department suggests retesting to make sure the first sample "was collected and analyzed properly." Which benchmark to use, and any health question, is for your state health department.

Health effects, in the agencies' own words

EPA's health-risk page (updated October 30, 2026) says "exposure to certain levels of PFAS may lead to" reproductive effects, developmental effects in children, "increased risk of some cancers, including prostate, kidney, and testicular cancers," reduced immune response "including reduced vaccine response," hormone interference, and "increased cholesterol levels and/or risk of obesity."

CDC's ATSDR (page dated July 22, 2025) names the compounds. It says "epidemiological evidence suggests associations" with:

• higher cholesterol (PFOA, PFOS, PFNA, PFDA)
• lower antibody response to some vaccines (PFOA, PFOS, PFHxS, PFDA)
• changes in liver enzymes (PFOA, PFOS, PFHxS)
• pregnancy-induced hypertension and preeclampsia (PFOA, PFOS)
• small decreases in birth weight (PFOA, PFOS)
• kidney and testicular cancer (PFOA)

ATSDR also says "scientists are still learning about the health effects of exposures to mixtures" and that "additional research may change our understanding."

EPA notes pregnant and lactating women "tend to drink more water per pound of body weight than the average person," and children drink and eat more per pound than adults. It also says "the benefits of breastfeeding appear to outweigh the risks for infants exposed to PFAS in breast milk," and advises mothers to talk to their doctors. On blood tests, Wisconsin DHS says "there isn't enough research to know at what PFAS levels you should expect health problems." If you're worried, take your water results to your doctor.

Treatment that works, and what doesn't

EPA names three home technologies: granular activated carbon, reverse osmosis and ion exchange resins. Minnesota's home-treatment page adds detail:

What doesn't work, per MDH: softeners and iron filters "are not likely to remove PFAS," and "boiling water will not remove PFAS." MDH also says point-of-use treatment "tends to be more economical than point-of-entry."

Certification: read the claim, not the box

EPA says to look for certification to "NSF/ANSI 53" or "NSF/ANSI 58" for PFAS reduction and to confirm it in the certifier's product directory. It lists five accredited certifiers: CSA Group, IAPMO R&T, NSF, UL and WQA. Two limits apply. As of April 2024, "filter certifications focus on removing the chemicals PFOA and PFOS," and current standards "do not yet indicate that a filter will remove PFAS down to the levels EPA has now set." EPA puts filter prices at "as little as $20 or more than $1,000 (not including maintenance costs)," and warns that skipping filter changes "can increase your risk of exposure to PFAS." Testing the treated water shows whether it works, which is why New York requires that test before paying a rebate.

Which water to treat

Agencies agree on drinking water and baby formula, and differ on cooking, brushing teeth and bathing. EPA suggests other water for "drinking, preparing food, cooking, brushing teeth, preparing baby formula," and Vermont says the same above its MCLs. Wisconsin DHS says high-PFAS water can still be used "for bathing, brushing teeth, washing dishes, doing laundry," but not for rice, oatmeal or gelatin. Maine says cooking, bathing or watering the garden "is unlikely to be a concern unless your water levels of these chemicals are very high." Follow your own state's advice.

Public water data: context, not your well

EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5) tested public water systems for 29 PFAS from January 2023 through December 2025. The final data summary (EPA 815-S-26-007, July 2026) compared system averages with the 2024 MCLs: "A weighted estimate of the total PWSs nationwide with one or more RAA greater than a PFAS NPDWR MCL is 7.8%." Large systems fared worst, and PFOS and PFOA exceeded far more often than the other four.

Three caveats. UCMR 5 covered only community and non-transient non-community systems, so no private wells are in it. EPA says the results "do not indicate compliance or noncompliance with the MCLs." And the USGS notes public wells "are usually deeper than private wells." If a public system near you found PFAS, take it as a reason to ask your health department about your area, not as a reading of your well.

A plan for your well

1. Ask what's known locally. Call your state or county health department. Wisconsin's PFAS Interactive Data Viewer and Minnesota's Groundwater Contamination Atlas are named on their state pages.
2. Check for free testing through New York's pilot or Wisconsin's WisPPWT.
3. If you pay, ask four things: the method (533, 537.1 or both), the compound list, the PFOA and PFOS reporting limits (ideally at or below 4 ng/L), and whether a field reagent blank is included.
4. Sample untreated water, exactly as the lab instructs.
5. Compare with your state's benchmark and EPA's, and retest a high result before acting.
6. If you treat, buy certified, maintain it, and test the treated water.
7. Keep up the yearly basics. Our which-tests tool builds the full list.

State pages: Maine, Vermont, New York, Wisconsin, Minnesota. We'll update this page when EPA finalizes, changes or withdraws its 2026 proposals.

Questions people ask