PFAS in Drinking Water — What Treatment Actually Helps

What are PFAS, and are there limits for drinking water?

PFAS — per- and polyfluoroalkyl substances — are a large family of man-made chemicals that do not break down easily, which is why they turn up in water supplies long after they were used. They are hard to take out at a treatment plant for the same reason the study we review below gives: their chemistry makes them difficult to separate from water [1].

In April 2024 EPA set enforceable drinking-water limits of 4.0 parts per trillion each for the two best-known ones, PFOA and PFOS [3][4]. In May 2026 EPA said it will keep those two limits and proposed to rescind the limits it had set for four others (PFHxS, PFNA, HFPO-DA — "GenX" — and a mixture measure), and to let water systems ask for two more years, to 2031, to comply [4]. Those are proposals; the current state of the rule is on EPA's page, not here.

What kind of water filter removes PFAS?

Three technologies reduce PFAS: activated carbon, ion exchange resin and reverse osmosis [2][3].

EPA names the same three families for a treatment plant and for a kitchen [2][3]. Activated carbon: PFAS stick to the carbon until there is no room left, and then the carbon has to be changed. Ion exchange resin: charged beads trade harmless ions for PFAS — the same principle as a softener, which trades sodium for calcium, only with the opposite charge [3]. Reverse osmosis: water is pushed through a membrane that holds the PFAS back and sends them to the drain in a reject stream [3].

Two things follow from how they work. Carbon and resin fill up, silently — nothing on the outside of a spent cartridge tells you it has stopped working. And carbon can be crowded out: EPA notes that other, "stickier" substances in the water can displace PFAS that the carbon had already caught [3].

Do home water filters actually remove PFAS?

Some remove nearly all of it and some much less. In a peer-reviewed test of the filters in 73 homes, every under-sink reverse osmosis and two-stage unit removed nearly all the PFAS measured, while other carbon filters were variable [1].

Researchers at Duke University and North Carolina State University tested the filters people already had at home — 73 homes in central and southeastern North Carolina — for sixteen different PFAS, and published the results in Environmental Science & Technology Letters in 2020 [1].

Under-sink reverse osmosis and under-sink two-stage filters: every one tested showed near-complete removal of every PFAS evaluated [1].

Every other filter with activated carbon — pitchers, countertop units, faucet-mounted filters, refrigerator filters, single carbon blocks under the sink — was variable. Longer-chain PFAS came out at roughly 60–70 %, shorter-chain ones at roughly 40 % [1].

Whole-house activated carbon systems: eight were tested, results were variable, and in four of the eight the filtered water had higher PFAS levels than the water going in [1]. The researchers also pointed out that a whole-house carbon system removes the disinfectant from all the pipes after it, which leaves those pipes open to bacterial growth [5].

Two honest limits. It is one study, in one state, of filters in whatever condition their owners kept them — which is the real-world question, but not a laboratory test of a new cartridge. And the university's summary gives the carbon filters an average of 73 % removal — an average that hides the spread the researchers describe: complete removal in some homes, no reduction at all in others [5].

How do I read a PFAS filter’s certification?

EPA's advice is short: find out which PFAS, if any, are in your water first — your water provider will tell you — then choose a filter certified to NSF/ANSI 53 or NSF/ANSI 58 with a claim for PFAS reduction [2]. Standard 53 covers filters for health-effect contaminants; 58 covers reverse osmosis systems.

One caution EPA states plainly: the current certifications do not yet show removal all the way down to EPA's new drinking-water limits [2]. A certified filter is a meaningful reduction, not a promise of a number.

And the part that is easiest to forget: EPA says a filter only works if it is maintained to the manufacturer's instructions, and that not replacing it on schedule can increase your exposure [2].

• First: ask your water provider, or read its annual water quality report
• Look for NSF/ANSI 53 or 58, with PFAS named in the claim
• Under-sink RO or two-stage for the water you drink and cook with
• Put the cartridge change date on the calendar the day it goes in

Does a whole-house filter remove PFAS?

Not reliably: in the same study, four of the eight whole-house carbon systems had more PFAS after the filter than before [1]. That does not make a whole-house filter pointless — it is doing a different job. A whole-house carbon system is what takes the chlorine taste and smell out of every tap and the shower, and a softener in the same line is what stops scale. Those are real problems and a point-of-entry system is the right tool for them.

For PFAS specifically, the evidence we have points to the kitchen tap: a point-of-use unit sized for drinking and cooking water, where the study found the consistent results [1]. That is also where reverse osmosis belongs anyway, because it sends part of the water to the drain [3].

What this means in Tampa Bay

Whether PFAS are in your water is a question for a test, not for a guess. On city water, your utility's annual water quality report is the first place to look; EPA's first step is the same [2]. On a private well, nobody tests it for you.

Most garages we work in here already have something on the wall — a softener for the hardness, sometimes a carbon tank for taste. If PFAS are a concern, the addition that the evidence supports is usually small: a certified under-sink unit at the kitchen. We install whole-house treatment and drinking-water systems, and we service what is already there, including equipment somebody else installed.

FAQ

Sources

We review and cite. We do not reproduce a paper or a manual — follow the links for the originals.

1. [1]Assessing the Effectiveness of Point-of-Use Residential Drinking Water Filters for Perfluoroalkyl Substances (PFASs) — Herkert NJ, Merrill J, Peters C, Bollinger D, Zhang S, Hoffman K, Ferguson PL, Knappe DRU, Stapleton HM · Environmental Science & Technology Letters 7(3):178–184 · 2020Peer-reviewed · 73 homes; under-sink RO and two-stage: near-complete removal; other carbon filters ~60–70 % long-chain, ~40 % short-chain; 4 of 8 whole-house carbon systems raised PFAS
2. [2]Reducing PFAS in Your Drinking Water with a Home Filter — US Environmental Protection Agency · 2026Government or standards body · carbon, ion exchange and RO; NSF/ANSI 53 or 58; certifications do not yet show removal to the new limits; replace on schedule
3. [3]Treatment Options for Removing PFAS from Drinking Water (fact sheet) — US Environmental Protection Agency · 2024Government or standards body · how GAC, anion exchange and RO work; displacement by other contaminants; reject stream
4. [4]Per- and Polyfluoroalkyl Substances (PFAS) — drinking water regulation — US Environmental Protection Agency · 2026Government or standards body · 4.0 ppt for PFOA and PFOS kept; May 2026 proposal to rescind four other limits and allow extension to 2031
5. [5]Not all in-home drinking water filters completely remove toxic PFAS — Duke University (news release, via EurekAlert!) · 2020University publication · the researchers' own summary: 73 % average for carbon filters; whole-house systems remove disinfectant from the pipes after them