PFAS in Drinking Water: What You Need to Know

PFAS are man-made chemicals, a family of nearly 15,000 of them, used in industry and in everyday products since the 1940s: stain and water repellent on carpet and clothing, nonstick pans, food packaging and firefighting foam.

On city water, your utility's water quality report or EPA's nationwide test results may already show your PFAS number, for free. On a private well, only a lab test will tell you.

People call them forever chemicals because the carbon-fluorine bond at their core is one of the strongest there is, so they do not break down easily, and some build up in the body over time.

Where PFAS in water comes from

PFAS reaches drinking water from the places that made it, used it or threw it away. EPA names these sources:

• Factories that make or use PFAS, and their waste
• Firefighting foam, used in training and emergencies at airports, military bases, fire training sites, chemical plants and refineries
• Landfills and hazardous waste sites
• Biosolids: treated sewage sludge spread on farm fields as fertilizer

Drinking water is only one way PFAS gets into people. EPA also names household dust, cleaning products and paints.

How common PFAS is in tap water

USGS's 45% is an estimate from a model built on 716 taps it sampled. At least one PFAS turned up in 40% of the public-supply taps and 20% of the private wells, and the levels were about the same in both. That matches what I tell well owners who call: you find PFAS more often in city water than in wells, but 1 private well in 5 in that study had it.

What PFAS can do to your health

EPA says most people in the U.S. have been exposed to some PFAS, and most known exposures are relatively low. Studies EPA cites link certain PFAS, at certain levels, to:

• Higher cholesterol
• A weaker response to vaccines
• Low birth weight and other developmental effects in children
• Lower fertility, and high blood pressure in pregnancy
• Some cancers, including prostate, kidney and testicular cancer
• Interference with the body's hormones

In 2023 the International Agency for Research on Cancer (IARC) classified PFOA as carcinogenic to humans and PFOS as possibly carcinogenic. That rates how strong the evidence is, not how much risk comes with a given level. EPA says research is still under way on what long, low exposure does, especially in children.

Showering is not the worry. EPA says so little PFAS passes through the skin that showering, bathing and washing dishes are unlikely to raise your risk much. For each health effect and the studies behind it, see PFAS health effects.

The EPA limit for PFAS today

As of September 28, 2026, EPA's limit for PFOA and PFOS in public drinking water is 4.0 parts per trillion (ppt) each, and water systems must meet it by April 26, 2029. EPA set it at 4.0 ppt because that is the lowest level labs can reliably measure; its health goal for both is zero.

Key dates for the PFAS rule

• April 10, 2024: EPA finalized the first national PFAS limits for drinking water.
• May 14, 2025: EPA said it would keep the PFOA and PFOS limits, give utilities more time and undo the other limits.
• May 18, 2026: EPA proposed both changes: until April 26, 2031 for utilities that ask, and removing the PFHxS, PFNA, GenX and mixture limits. Comments closed July 20, 2026.
• September 18, 2026: The federal appeals court in Washington, D.C. heard the water utilities' challenge to the rule. It had not ruled as of September 28.
• April 26, 2027: Utilities must report their first PFAS results.
• April 26, 2029: Utilities must meet the limits, unless the 2031 extension is finalized and they are granted it.

Until 2029, the PFAS limits a utility can be held to are its state's, if its state has them. New Jersey, Massachusetts, Michigan, New Hampshire and Pennsylvania set their own before EPA did, and Vermont adopted EPA's limits on January 1, 2026. For contamination and limits state by state, see PFAS contamination by state.

How to read your PFAS number

On a PFAS lab report, parts per trillion (ppt) and nanograms per liter (ng/L) are the same unit. Some reports use parts per billion (ppb) instead, and 1 ppb is 1,000 ppt, so a small-looking decimal can be over the limit.

The last row is a number a well owner read me off a lab report in July. "Freaking PFAS is everywhere," the caller said. As parts per trillion it is 12.1, about three times EPA's limit if that compound is PFOA or PFOS.

Two more things to check. The 4.0 ppt limit applies to PFOA and PFOS one at a time, not added together. And a utility is judged on a running average of its samples over a year; one sample from your tap is a snapshot.

Have a PFAS lab report?

Text me your PFAS numbers

Send a photo of the results page. I will tell you which numbers are over EPA's limits and what I would do next.

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PFAS in city water

If you are on city water, your utility has to test for PFAS and tell you what it finds. Utilities must report their first PFAS results by April 26, 2027, and community systems put them in their annual water quality report (the Consumer Confidence Report) starting in 2027.

You may not have to wait. EPA's nationwide PFAS testing from 2023 to 2025, called UCMR 5, covered every community water system serving more than 3,300 people, plus 800 smaller systems, and EPA released the final results in August 2026. Look up your utility by name in EPA's UCMR 5 Data Finder. Utilities that found PFAS in that testing also had to list it in their water quality report.

A caller in Massachusetts had been getting quarterly postcards saying the town's PFAS was elevated, then heard the town had fixed it. I told the caller what that usually means: "They probably brought it down to EPA standard levels, which means there still could be PFAS in the water." Under the limit is not the same as none.

If the report says nothing, or you want your own tap measured: the city water test we sell does not include PFAS, and the PFAS test kit does.

PFAS in private well water

EPA's PFAS limits cover public water systems only, so a private well gets tested for PFAS when its owner has it tested. Two exceptions: New Jersey requires PFOA, PFOS and PFNA testing before a home with a well is sold, and landlords there must test every five years; and EPA may test private wells near a Superfund site it is investigating.

A well owner called me in September: "we are in an area that's been contaminated with PFAS ... Is there anything that can be done if it does ... test positive for PFAS?" Yes, and the first step is the test. If your well is near one of the sources above, test it first. MassDEP recommends testing every private well, especially one within one to two miles of a known PFAS source.

The complete well water test we sell does not measure PFAS. The PFAS test kit ($349) does: a lab in the SimpleLab network measures 14 PFAS by EPA Method 537.1, including PFOA, PFOS, PFHxS, PFNA and PFBS, and results come back about 10 business days after the lab receives your sample. It does not include GenX.

If your number comes back over the limit, EPA's advice to well owners is to consider other water for drinking, cooking and baby formula, and a home filter certified to lower PFAS.

What reduces PFAS in your water

Three kinds of home treatment reduce PFAS: reverse osmosis, activated carbon and PFAS resin, and each works only as long as its filter, membrane or media is replaced on time.

	Treatment	What it treats	What the research says	Price
	Under-sink reverse osmosis: forces water through a thin barrier	Drinking and cooking water at the kitchen tap	EPA: typically more than 90% effective on a wide range of PFAS, smaller ones included. Uses about 1 gallon of water for every gallon it makes.	$595 (Pure-75)
	Whole-house carbon tank: activated carbon on the main line	Every tap in the house	EPA: works well on bigger PFAS like PFOA and PFOS, less well on smaller ones like PFBS.	$1,495 for the 1.5 cubic foot tank, $1,695 for the 2.5
	PFAS resin tank: a tank of beads made to grab PFAS (ResinTech SIR-110-HP)	Every tap in the house	EPA: this kind of resin has a high capacity for many PFAS. When the beads are used up they are replaced; salt cannot recharge them the way it does a softener's.	$2,495
	Whole-house PFAS cartridge: a large filter cartridge in a blue housing (Pentair FloPlus Protect 20BB)	Every tap, up to 5 gallons per minute	Certified to reduce 5 PFAS, including PFOA and PFOS (NSF/ANSI 53, by IAPMO R&T). 40,000 gallons per cartridge.	$349

Changing media on time is not optional. In a 2020 Duke and NC State study of home filters, every under-sink RO cut PFAS by 90% or more, but 4 of 6 whole-house carbon systems had more PFAS after the filter than before, which the researchers said suggests spent carbon giving it back. Whatever you install, test the treated water afterward to make sure it is working, as Minnesota's health department advises.

For a whole house, which one fits depends on which PFAS your test shows and how high they are, and that is the call I make with people once they have a lab report. How to weigh carbon, resin and RO against each other is its own page: choosing a PFAS water filter.

Which PFAS filters are certified

None of the whole-house tanks or reverse osmosis units we sell is certified to reduce PFAS. The one PFAS-certified item we sell is the Pentair FloPlus Protect 20BB cartridge: IAPMO R&T lists it under NSF/ANSI 53 for five PFAS (listing W-13717). EPA says to look for NSF/ANSI 53 or 58 certification for PFAS reduction on the label, and notes that today's certifications do not yet show a filter will bring PFAS down to its new 4.0 ppt limit.

What does not remove PFAS

Boiling, water softeners and iron filters do not remove PFAS, according to Minnesota's health department. Sediment filters and UV lights are not PFAS treatment either: one catches particles, the other kills germs.

Frequently asked questions