Many Bexar County residents notice subtle but persistent water quality issues at their taps despite having treatment systems already in place. This page focuses on PFAS (per- and polyfluoroalkyl substances), a class of fluorinated compounds sometimes referred to as 'forever chemicals' due to their environmental persistence, and addresses key questions about regional measurements and treatment approaches for these substances in household water.
How does the UCMR5 survey differ from UCMR3 in compounds monitored and detection levels?
The current federal Unregulated Contaminant Monitoring Rule 5 (UCMR5) conducted between 2023 and 2026 samples public water systems including San Antonio Water System in Bexar County for a broader range of PFAS compounds than the previous UCMR3. While UCMR3 focused primarily on PFOA and PFOS, UCMR5 also includes PFHxS, PFNA, HFPO-DA, PFBS, PFHxA, PFPeA, PFBA, and PFHpA among others. Detection limits in UCMR5 are lower, in the thousandths of micrograms per liter (µg/L), allowing identification of even trace amounts of these substances not captured previously.
Why are PFOA and PFOS measured in nanograms per liter and what does four-decimal precision indicate?
PFAS compounds like PFOA and PFOS are reported in nanograms per liter (ng/L), equivalent to parts per trillion (ppt), reflecting their presence at extremely low concentrations in water. Reporting results with four decimal places (e.g., 0.004 µg/L) provides high precision, ensuring that even minuscule amounts are recorded. This precision aids regulators and consumers in understanding background levels and evaluating emerging health benchmarks, like the 2024 federal maximum contaminant level (MCL) of 4 ng/L for PFOA and PFOS.
Why are granular activated carbon beds and ion-exchange resins documented differently for PFAS treatment?
Granular activated carbon (GAC) beds and ion-exchange resins represent two documented technologies for reducing PFAS concentrations in water. GAC primarily adsorbs longer-chain PFAS compounds, while ion-exchange resins can target a broader range of these substances including some shorter-chain variants. Each functions through different chemical mechanisms and is documented as such, influencing their effectiveness depending on the PFAS compounds present and household water demand.
What role do plumbing material and age play separate from source water PFAS levels?
While the San Antonio Water System's source water is surface water with documented PFAS results, household plumbing materials and age can impact water quality independently. Older pipes or certain fixtures might contribute to aesthetic or secondary water quality issues unrelated to PFAS. Understanding this distinction is important because regional PFAS data does not capture these internal plumbing factors, which require separate evaluation.
What considerations arise for large households, second homes, or seasonal water use?
Households with higher daily water demand, multiple residences, or intermittent occupancy may find existing equipment insufficient to consistently reduce PFAS levels as water use patterns influence filter performance and longevity. Treatment solutions must be capable of handling fluctuating flow and volume without compromising PFAS reduction efficiency, making documented system capacity and configuration critical factors for these situations.
In summary, the San Antonio Water System serving Bexar County shows no detections of PFOA, PFOS, PFHxS, PFNA, or HFPO-DA above reporting levels and within upcoming federal MCLs. Low-level detections of PFBS, PFPeA, and PFBA occur but remain well below health benchmarks. These measurements inform residents about regional fluorinated compound presence but do not indicate individual household water quality. Testing of a home's water is necessary for specific assessment.
The Autotrol PFAS Forever Chemicals Filter system is a documented technology designed to reduce a broad range of PFAS compounds from household water. It ships ready to configure for residential use, providing an option for households seeking to supplement existing equipment that may be struggling to keep pace with household water demand or emerging PFAS concerns.
All referenced water quality data comes from the EPA's public water system records for the San Antonio Water System (CWS ID TX0150018), accessible via the EPA's online UCMR database.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2026-06-16. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for SAN ANTONIO WATER SYSTEM (TX0150018), TX: 910 results across 10 listed contaminants, 6 detections above the reporting level; compared with the applicable federal MCL, none above
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