Is there PFAS in Stillwater Water Plant water?
Yes. EPA's final UCMR 5 results show Stillwater Water Plant averaged 6.1 ppt of PFOS at its worst sampling point, 1.5 times the EPA limit of 4 ppt.
Stillwater Water Plant
Serves 53,000 people · 4 PFOA samples from 1 sampling point · Dec 2023 to Sep 2024
Average above an EPA limit
PFOA Perfluorooctanoic acid
not detected
PFOS Perfluorooctanesulfonic acid
6.1 ppt avg · max 8.6
PFHxS Perfluorohexanesulfonic acid
4.6 ppt avg · max 6.4
Hazard index GenX, PFBS, PFNA, PFHxS combined
0.5 avg · max 0.6
Also detected, no federal limit: PFHxA, PFPeA, PFBS.
Stillwater Water Plant is a public water system drawing on surface water, based in Stillwater, Oklahoma, serving about 53,000 people. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 4 times across 1 sampling point between Dec 2023 and Sep 2024.
Every PFAS detected
Not detected: 8:2 FTS, 4:2 FTS, 6:2 FTS, PFBA, HFPO-DA, ADONA, 11Cl-PF3OUdS, PFDoA, PFDA, PFOA, PFNA, PFMPA, PFHpA, 9Cl-PF3ONS, PFUnA, PFMBA, PFEESA, NFDHA, PFPeS, PFHpS, NMeFOSAA, PFTA, NEtFOSAA, PFTrDA.
Lithium, tested in the same program: highest 21.6 ppb, detected in 4 of 4 samples. EPA's health-based screening level is 10 ppb.
What the EPA limits mean here
In April 2024 EPA set enforceable limits of 4 ppt for PFOA and PFOS, 10 ppt each for PFHxS, PFNA and GenX, and a hazard index of 1 for mixtures. Utilities were given until 2029 to comply. In May 2026 EPA proposed keeping only the PFOA and PFOS limits and moving that deadline to 2031. Until that proposal is final, the 2024 limits stand.
Compliance is judged on a running annual average at each entry point, so we show the average at this system's worst sampling point next to its single highest result. UCMR 5 results do not by themselves put a utility in or out of compliance.
What you can do at home
Two routes work for PFAS. For drinking and cooking water only, a reverse osmosis system certified to NSF/ANSI 58 with a PFOA/PFOS reduction claim is the cheapest proven option. To treat every tap and shower, a whole-house carbon system with enough contact time works, but check that the maker has PFAS test data, not just a marketing claim. See the best filters for PFAS and how PFAS removal works.
Other systems in Oklahoma
All 166 tested systems in Oklahoma
ZIP codes served
74074
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Cite this page
Well & Tap. "PFAS in Stillwater Water Plant water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID OK1021220. https://wellandtap.com/pfas/oklahoma/stillwater-water-plant/
About this data
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID OK1021220). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
