PFAS in well water
PFAS are man-made chemicals that break down very slowly and turn up in nearly half of U.S. tap water. The EPA limit for PFOA and PFOS in public water is 4.0 ng/L each. A PFAS test costs about $250 to $500. A filter certified for PFOA and PFOS at the kitchen sink handles most of your exposure.
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What you need to know about PFAS
| The limit | 4.0 ng/L each for PFOA and PFOS (nanograms per liter, the same as parts per trillion). This is the EPA limit for public water. The EPA's health goal for both is 0. |
|---|---|
| Who it hurts | Long-term exposure is linked to some cancers, higher cholesterol, weaker vaccine response, and low birth weight and other effects in children. |
| Where it comes from | Factories that made or used PFAS, firefighting foam, waste sites, and everyday products such as nonstick pans and stain-resistant fabric. |
| How often to test | At least once if you live near a likely source. The EPA suggests regular well testing, and your state health or environment agency can give advice and a list of certified labs. |
| What removes it | Reverse osmosis, activated carbon or ion exchange filters certified to NSF/ANSI 53 or 58 for PFOA and PFOS. |
| What a test costs | About $250 to $500 per sample, according to Penn State Extension. Few labs are accredited to run it. |
PFAS reach groundwater near factories, waste sites and foam spills
PFAS are a family of thousands of man-made chemicals. The EPA says they've been used since the 1940s in nonstick cookware, food packaging, waterproof clothing, stain-resistant furniture and firefighting foam. They break down very slowly, so people call them "forever chemicals."
The EPA lists the main sources in drinking water as factories and chemical plants, consumer products, workplace exposure, and some firefighting activities. Penn State Extension says PFAS dissolve easily in water and don't break down in soil, so they can move from these sites into groundwater. Wells near military bases, fire training sites, dumps, landfills, factories and fields spread with contaminated biosolids are more likely to have them.
They're common. A 2023 USGS study estimated that at least 45% of U.S. tap water has 1 or more PFAS, and levels were similar in private wells and public systems. Most detections were near cities and known sources, in the Great Plains, Great Lakes, Eastern Seaboard and central and southern California. USGS put the chance of finding no PFAS at about 75% in rural areas and 25% in urban ones.
Health risks come from years of exposure
The EPA links PFAS exposure to:
- Higher risk of prostate, kidney and testicular cancer
- Higher cholesterol
- A weaker immune response, including to vaccines
- Low birth weight and other effects on children's growth and development
- Lower fertility and high blood pressure during pregnancy
- Changes in the body's hormones
Researchers are still working out the long-term effects. The EPA set its health goal for PFOA and PFOS at 0.
In April 2024 the EPA set limits for 6 PFAS in public water: 4.0 ng/L each for PFOA and PFOS, 10 ng/L each for PFHxS, PFNA and GenX, and a combined limit for mixtures.
In May 2025 the EPA announced it would keep the PFOA and PFOS limits and reconsider the other 4. In May 2026 it proposed 2 rules to do that. One keeps PFOA and PFOS at 4.0 ng/L and gives water systems 2 more years, to 2031, to comply. The other would remove the limits for PFHxS, PFNA, GenX and the mixture.
None of these rules cover private wells. The EPA doesn't regulate them.
Testing takes a special lab
PFAS show up at parts per trillion, so testing needs specialized lab equipment. Penn State Extension says a test costs about $250 to $500 per sample, and Pennsylvania had only a handful of labs accredited for it.
Ask for EPA Method 533, which covers 25 PFAS, or Method 537.1, which covers 18. Both include the ones in the federal rule. The lab sends special bottles and instructions for collecting, handling and shipping the sample. Follow them exactly.
Before you pay, check with your state. Colorado offers free PFAS testing to any private well owner while supplies last, and free filters to some households.
A certified filter at the kitchen sink handles most of it
Penn State Extension says most PFAS exposure from well water comes from drinking it, with little through skin contact. A filter at the tap you drink from covers most of that risk.
Look for certification to NSF/ANSI 53 (filters) or NSF/ANSI 58 (reverse osmosis) with a claim for "PFOA reduction" and "PFOS reduction." The EPA notes that as of April 2024 these certifications didn't yet prove a filter gets water down to 4.0 ng/L. Any certified reduction still lowers your exposure.
| Option | Typical cost | Replacement parts |
|---|---|---|
| Certified pitcher | $25 to $75 | $15 to $45 every 3 to 6 months |
| Countertop or under-sink carbon or ion exchange | $400 to $1,636 | $60 to $260 or more, every 6 to 12 months |
| Under-sink reverse osmosis | $450 and up | $120 and up; carbon every 6 to 12 months, membrane every 12 to 24 |
| Whole-house carbon or anion exchange | $500 to $1,500 | Media replaced on a schedule |
Costs are from Penn State Extension's PFAS treatment guide and its general equipment guide.
Change filters on schedule. The EPA says an old filter can let PFAS through and raise your exposure.
Questions people ask about PFAS
Do I need to worry about PFAS in the shower?
Penn State Extension says most PFAS exposure from water comes from drinking it, with little through the skin. That's why a filter at the kitchen tap is the usual first step.
Does a pitcher filter work for PFAS?
Some do. Only use one certified to NSF/ANSI 53 for PFOA and PFOS reduction. The EPA says not all filters address PFAS.
Is the EPA getting rid of the PFAS limits?
Not for PFOA and PFOS. EPA's 2026 proposal keeps them at 4.0 ng/L and gives water systems until 2031. It would drop the limits for 4 other PFAS. These rules apply to public water, not private wells.
Why does a PFAS test cost so much more than other tests?
PFAS are measured in parts per trillion. Penn State says that takes complex instruments and long lab methods, and few labs are accredited to do it.
Where this comes from
- U.S. EPA, Per- and Polyfluoroalkyl Substances (PFAS) drinking water regulation
- U.S. EPA, National Primary Drinking Water Regulations
- U.S. EPA, Our Current Understanding of the Human Health and Environmental Risks of PFAS
- U.S. EPA, Reducing PFAS in Your Drinking Water with a Home Filter
- U.S. EPA, Meaningful and Achievable Steps You Can Take to Reduce Your Risk
- USGS, Tap water study detects PFAS 'forever chemicals' across the US
- Penn State Extension, PFAS Drinking Water Standards, Testing and Treatment
- Penn State Extension, Home Water Treatment for PFAS
- Penn State Extension, Tips for Buying Water Treatment Equipment
- Colorado Department of Public Health and Environment, PFAS Testing and Assistance Program