EPA UCMR5 testing detected PFAS in San Antonio's drinking water at levels below current federal limits but above what many health experts recommend. San Antonio Water System (SAWS) serves over 2 million people across Bexar County. In KYE's analysis of the EPA data, the main SAWS system had no detectable PFOA or PFOS; the compounds that did show up were short-chain PFAS (PFBA, PFBS and PFPeA).
San Antonio Water System provides water to more than two million people in San Antonio and nearby suburbs. Under EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR5), SAWS tested for 29 different PFAS compounds between 2023 and 2025, sampling 29 entry points in its main system.
The results show detectable levels of PFAS, but the picture is more complex than a simple yes-or-no answer.
UCMR5 testing identified a few PFAS compounds in San Antonio's water supply. In the main SAWS system (PWSID TX0150018), KYE's analysis of the EPA data shows:
PFBA (perfluorobutanoic acid): Detected in several samples, up to 9.2 parts per trillion (ppt). PFBA is a short-chain PFAS with no federal limit.
PFBS (perfluorobutanesulfonic acid): Detected up to 3.8 ppt. The 2024 rule counted PFBS only inside a mixture Hazard Index, with a health-based value of 2,000 ppt.
PFPeA (perfluoropentanoic acid): Detected once, at 3.2 ppt. No federal limit.
PFOA, PFOS, PFHxS and PFNA: Not detected in the main SAWS system. The EPA limit for PFOA and PFOS is 4.0 ppt each.
The exception is the separate SAWS Castle Hills system (TX0150045), where one sample showed PFOS at 4.0 ppt, right at the federal limit, plus PFBS at 3.2 ppt. Local reporting in 2024 traced that reading to a single Castle Hills well.
San Antonio's water comes mainly from the Edwards Aquifer, which supplies over half of it, plus the Trinity and Carrizo aquifers, the Vista Ridge pipeline and a brackish groundwater desalination plant, according to SAWS. UCMR5 results are reported by entry point, not by aquifer, so the data doesn't show which source carries the short-chain PFAS.
When several PFAS compounds turn up together, individual readings below their limits can still add up. EPA's 2024 rule used a hazard-index approach for mixtures of PFHxS, PFNA, HFPO-DA, and PFBS. In the main SAWS system, only PFBS among those four was detected, at a tiny fraction of its 2,000 ppt health-based value, so the hazard index sits far below 1.
Texas has no state-level PFAS drinking water limits beyond federal requirements. This means San Antonio follows EPA rules but isn't subject to separate state limits like those in New Jersey or Michigan.
While San Antonio's PFAS levels are low compared to industrial contamination sites, they're not zero. For context:
The gap between EPA's regulatory limits and what some health researchers recommend creates confusion. Meeting federal standards doesn't necessarily mean zero health risk – it means the EPA has balanced health protection with technical feasibility and cost.
PFAS levels vary by treatment facility and water source. UCMR5 testing was done at each system's entry points, not at individual taps, and EPA does not publish which ZIP codes each entry point serves. So there is no reliable public ZIP-by-ZIP PFAS ranking for San Antonio.
What the data does show, by water system (KYE analysis of EPA UCMR5 data):
SAWS main system (most of San Antonio): - PFBA up to 9.2 ppt, PFBS up to 3.8 ppt, PFPeA up to 3.2 ppt - No PFOA, PFOS, PFHxS or PFNA detected
SAWS Castle Hills system: - PFOS at 4.0 ppt in one sample, PFBS at 3.2 ppt
City of Leon Valley: - PFBS at 3.1 ppt
Your actual exposure depends on which water system and entry point serve your address, seasonal blending of water sources, and your building's plumbing. Check your water quality by zip code to see which systems serve your area.
PFAS doesn't appear in water naturally. It gets there through:
Industrial discharge: Aerospace, metal finishing and other manufacturing have historically used PFAS in production processes.
Military bases: Joint Base San Antonio (Lackland, Fort Sam Houston, Randolph) used PFAS-containing firefighting foam, like military installations nationwide, and the Department of Defense is investigating PFAS releases at its bases.
Wastewater treatment: PFAS passes through conventional wastewater plants largely unchanged and re-enters rivers downstream.
Airport firefighting: US commercial airports were required to keep PFAS-containing AFFF (aqueous film-forming foam) for firefighting until the FAA approved fluorine-free alternatives in 2023.
Once PFAS enters groundwater, it moves slowly but persistently. The Edwards Aquifer is particularly vulnerable because it's a karst system with rapid recharge – what goes in at the surface can reach drinking water wells relatively quickly.
When the EPA finalized its PFAS rule in April 2024, SAWS said in a statement that there was no indication treatment was necessary for the regulated compounds, according to San Antonio Report. The utility said it:
Utilities that do need PFAS treatment typically use granular activated carbon (GAC), ion exchange or reverse osmosis, all of which EPA lists as effective.
SAWS publishes water quality data on its website, including its annual Consumer Confidence Report. These reports don't break down PFAS results by neighborhood or zip code.
If you're served by a system with detections or just want to reduce exposure:
Point-of-use filtration works. Reverse osmosis systems certified to NSF/ANSI 58 remove 90%+ of PFOA and PFOS. Activated carbon filters vary widely: look for NSF/ANSI 53 certification for PFAS (for example, PUR PLUS pitcher filters), since standard Brita pitcher filters are certified only for taste and odor (NSF 42). Short-chain PFAS like PFBA are harder for carbon to capture than PFOA or PFOS. We compared best water filters for PFAS if you want specific product recommendations.
Avoid non-stick cookware and stain-resistant treatments. PFAS in drinking water is one exposure route, but cookware and treated fabrics can contribute similar or higher amounts. Cast iron and stainless steel don't leach PFAS.
Don't boil PFAS out. Boiling water kills bacteria but concentrates PFAS. If you're boiling for safety, that's fine – just know it won't reduce forever chemicals.
Pregnant women and young children: These groups are considered most sensitive to PFAS. Consider a certified point-of-use filter if your system shows PFOS or PFOA detections.
EPA's new PFAS regulations took effect in 2024. Water systems have until 2029 to comply with the 4.0 ppt limits for PFOS and PFOA individually, plus hazard index limits for mixtures of other PFAS. (In May 2026, the EPA proposed dropping the hazard index and other non-PFOA/PFOS limits and letting systems extend the PFOA/PFOS deadline to 2031.)
Based on the UCMR5 data, the main SAWS system already meets the PFOA and PFOS limits; the Castle Hills well sits right at the PFOS limit, and compliance is judged on running annual averages. Meeting the regulatory limit doesn't mean PFAS goes away entirely – short-chain compounds like PFBA have no federal limit.
Texas hasn't indicated plans for state-level limits stricter than EPA's. Until that changes, San Antonio's water quality is governed by federal standards.
For now, the best way to know your exposure is to check your specific zip code. PFAS levels vary by water system, and our tool maps EPA data to the systems that serve your zip code.
San Antonio's main SAWS system had no detectable PFOA or PFOS in EPA's UCMR5 testing, but did show low levels of short-chain PFAS (PFBA, PFBS, PFPeA) that exceed what some health experts recommend. The separate Castle Hills system had one PFOS reading at the 4 ppt limit. If you're concerned about exposure, point-of-use filtration reduces PFAS significantly. Check your water quality to see actual contamination data for your address.
Is San Antonio water safe to drink with PFAS in it? San Antonio's main SAWS system had no detectable PFOS or PFOA in EPA's UCMR5 testing, and the one Castle Hills PFOS reading was at, not above, the 4.0 ppt limit. However, short-chain PFAS such as PFBA (up to 9.2 ppt) were detected, and some health researchers recommend keeping total PFAS below 1 ppt. The water is legally safe but reducing exposure through filtration is an option if you're concerned.
Which San Antonio neighborhoods have the highest PFAS levels? EPA's UCMR5 data is reported by water system and entry point, not by neighborhood, so there is no reliable public ZIP-level ranking. By system, the only PFOS detection was in the separate SAWS Castle Hills system (4.0 ppt in one sample); the main SAWS system showed only short-chain PFAS. Check your specific zip code to see which systems serve it.
Does boiling San Antonio water remove PFAS? No. Boiling kills bacteria but concentrates PFAS because the chemicals don't evaporate. To remove PFAS, use a reverse osmosis system certified to NSF/ANSI 58 or a carbon filter certified to NSF/ANSI 53 for PFAS.
Where does PFAS in San Antonio water come from? The specific sources of the low PFAS levels in San Antonio's water haven't been publicly traced. Common sources in any metro area include firefighting foam used at military bases (such as Joint Base San Antonio) and airports, industrial facilities, and wastewater discharge.
What is SAWS doing to reduce PFAS levels? After the 2024 EPA rule, SAWS said there was no indication treatment was necessary for the regulated compounds. It blends water from multiple wells and sources, which dilutes contaminants, and said it would take any well that exceeds the limits out of service.
You can Check your water quality by zip code to see if your area is affected. If you're looking for solutions, Find water filters that remove PFAS certified for removal. Check your state's water quality to compare contamination levels across the country.
Check your water now. Enter your zip code at KnowYourExposure.com to see what contaminants have been detected in your local water supply – including PFAS, lead, and other regulated compounds.