Contaminants
PFAS in Charleston Drinking Water
EPA’s own monitoring data, the utilities’ own reports, and the one piece of equipment that addresses it.
EPA’s own monitoring data, the utilities’ own reports, and the one piece of equipment that addresses it.
Quick answer: EPA’s monitoring found PFOS above the new federal limit of 4.0 parts per trillion at every surface-water system in the Charleston tri-county, and PFOA above it at most. Charleston Water System measured PFOA 4.3 and PFOS 5.8. These limits are legally in force but not enforceable until April 2029, so no utility is in violation. Point-of-use reverse osmosis is the treatment with real evidence behind it. Call (843) 718-8177.
PFAS are a family of manufactured chemicals used since the 1940s in non-stick coatings, firefighting foam, stain-resistant fabric and a great deal else. They are called forever chemicals because they do not meaningfully break down.
In April 2024 EPA set the first enforceable federal drinking-water limits for them. That is the context for everything below, and the dates matter as much as the numbers.
PFOA and PFOS are each limited to 4.0 ppt. PFHxS, PFNA and GenX are limited to 10 ppt each, covering PFHxS, PFNA and HFPO-DA (GenX), plus a Hazard Index of 1.
Water systems must complete initial monitoring by April 2027 and comply by April 2029 (EPA PFAS drinking water regulation).
EPA proposed extending the PFOA/PFOS deadline to 2031 and rescinding the other four limits (both published 2026-05-20, comments closed 2026-07-20). Neither is final. The six limits remain in force.
You will find pages saying the deadline is 2031. It is not, yet. ⚠️ We will update this page if that changes (EPA proposed PFOA/PFOS compliance extension).
These are entry-point averages from EPA’s own monitoring dataset. We cross-checked Charleston Water System’s figures against the utility’s own published report and they match exactly.
| System | PFOA / PFOS | Over the 4.0 limit? |
|---|---|---|
| Charleston Water System | 4.3 / 5.8 | Yes |
| Mount Pleasant — purchased Charleston water | 3.6 / 6.6 | Yes |
| Mount Pleasant — its four reverse-osmosis well plants | not detected / not detected | No |
| Isle of Palms — Charleston connection | 1.4 / 6.8 | Yes |
| Isle of Palms — its deep-well RO plant | not detected / not detected | No |
| Folly Beach | 4.5 / 6.5 | Yes |
| Kiawah Island Utility | 3.2 / 6.3 | Yes |
| Seabrook Island | 2.4 / 6.7 | Yes |
| St. John's Water Company | 4.9 / 7.2 | Yes |
| Summerville CPW | 5.7 / 6.7 | Yes |
| Dorchester County Water & Sewer — Ashley Phosphate | 5.7 / 6.6 | Yes |
| Moncks Corner | 5.2 / 6.8 | Yes |
| Goose Creek | 5.2 / 6.0 | Yes |
| Berkeley County — Sangaree | 5.8 / 6.3 | Yes |
| Berkeley County — East Cooper | 5.4 / 6.6 | Yes |
Source: EPA UCMR5 occurrence data. No utility here is in violation — the limits do not become enforceable until April 2029, and every one of these systems is working to a deadline it has not yet reached.
PFAS is in the surface water and it is not in the wells. Every groundwater entry point tested in the tri-county came back non-detect for both compounds.
Mount Pleasant’s four reverse-osmosis well plants: non-detect. Isle of Palms’ deep-well plant: non-detect. The same utilities’ purchased Charleston water: over the limit. It is the source, not the town.
Nationally, EPA found about 12% of large water systems over the PFOS limit. In the Charleston tri-county, every surface-water system tested over it.
⚠️ One honest caution about Mount Pleasant specifically: its own published report appears to label its PFAS results as coming from RO-treated groundwater, but EPA’s raw data shows those values came from its Charleston purchased-water connection while the RO plants were non-detect. We do not republish that table.
Duke and NC State tested 76 point-of-use filters and 13 whole-house systems, tested in real North Carolina homes. Reverse osmosis and two-stage under-sink filters reduced PFAS, including GenX, by 94% or more. Activated carbon filters removed 73% of PFAS on average, but results varied enormously, with no clear pattern by brand, filter age or source water.
In four of the six whole-house carbon systems tested, PFAS levels actually INCREASED after filtration. (Duke / NC State home filter study (Herkert et al., ES&T Letters))
NSF’s certified-product database lists 49 products certified for Total PFAS reduction and 60 for PFOA reduction. Every one is point-of-use — a counter-top unit, a plumbed-in unit or one plumbed to a separate tap, rated between 0.66 and 1.25 gallons per minute. There are no point-of-entry products with a PFAS certification.
Point-of-use reverse osmosis is the honest answer for PFAS. A whole-house carbon tank is genuinely good at chloramine, taste, odour and disinfection byproducts, which is what it should be sold for here. Anyone selling a whole-house system as a PFAS solution is selling the wrong box.
| Technology | What the evidence shows | Source |
|---|---|---|
| Reverse osmosis | Typically more than 90% effective across a wide range of PFAS, including the short-chain compounds carbon struggles with. | EPA — reducing PFAS with treatment technologies · 2026-02-19 |
| Granular activated carbon | Can be highly effective for a period of time, but works well on longer-chain PFAS like PFOA and PFOS while shorter-chain compounds do not adsorb as well. | EPA — reducing PFAS with treatment technologies · 2026-02-19 |
| Anion exchange resin | Like carbon, removes essentially all PFAS for a time, then breaks through. | EPA — reducing PFAS with treatment technologies · 2026-02-19 |
| Water softeners and iron filters | Do not remove PFAS. Minnesota’s health department states this flatly, citing its own sampling data. | Minnesota Department of Health — PFAS home treatment · 2024-04-10 |
Certifications come in two vintages. The 2021 version of the standard allowed a filter to pass by reducing PFOA and PFOS to 70 parts per trillion. The 2022 version lowered that to 20 ppt total. Many products on sale are still certified to the older, weaker version — and both limits sit above EPA’s new 4.0 ppt standard.
EPA’s own guidance still carries this warning: “The current certification standards for PFAS filters do not yet indicate that a filter will remove PFAS down to the levels EPA has now set for a drinking water standard. EPA is working with standard-setting bodies to update their filter certifications.”
You can look any model up yourself in NSF certified drinking water treatment units database — it takes about a minute, and it is the single most useful thing a homeowner can do before signing anything.
Yes. EPA’s monitoring measured PFOA at 4.3 and PFOS at 5.8 parts per trillion in Charleston Water System’s water, both above the federal limit of 4.0.
Charleston Water System publishes the same figures in its own report. Every surface-water system in the tri-county tested above the PFOS limit — Summerville, Goose Creek, Moncks Corner, Berkeley County, Folly Beach, Kiawah, Seabrook and St John’s among them.
No Charleston-area water system has a health-based violation on EPA’s record, and the PFAS limits are not enforceable until April 2029.
That is the accurate answer and it is deliberately unexciting. The utilities are inside the law and working to a deadline. Whether you want to wait until 2029 for water you drink today is a separate decision, and it is yours.
Reverse osmosis, at the tap. EPA puts it at more than 90% effective across a wide range of PFAS; a field study of real homes found 94% or better.
Granular activated carbon works for a time and then breaks through, and performs poorly on short-chain compounds. Water softeners and iron filters do not remove PFAS at all.
Not reliably. In a field study of real homes, PFAS levels increased after filtration in four of six whole-house carbon systems tested.
There is also no point-of-entry system with an NSF certification for PFAS reduction — all 49 products certified for total PFAS reduction are point-of-use. If a company sells you a whole-house system as a PFAS solution, ask to see the certification for that model.
Water systems must complete initial monitoring by April 2027 and comply with the limits by April 2029.
EPA has proposed extending the PFOA and PFOS deadline to 2031 and rescinding the limits on three other compounds, but both are proposals — neither is final, and the six limits set in April 2024 remain in force.
Every groundwater entry point tested in the tri-county came back non-detect for PFOA and PFOS.
That is public-supply groundwater rather than private wells, so it is encouraging rather than conclusive for any individual well. Wells here have their own issues — see well water treatment.
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