CheckPFAS

ZIP Code 78666

Low Level
Low Level PFAS Risk Level
10
PFAS Detected
0
Above EPA Limits
4
Water Systems
34%
Highest % of MCL

MAXWELL WSC

TX0280003 Low Level
Water Type
Surface Water
PFAS Detected
3
Above MCL
0
State
Texas
Data Period
2023–2025

PFAS Test Results

CompoundDetectedvs. EPA LimitEPA LimitStatus
lithium
9800.00pptNo federal limit—Unregulated
PFPeA
Perfluoropentanoic acid
3.80pptNo federal limit—Unregulated
PFHxA
Perfluorohexanoic acid
3.70pptNo federal limit—Unregulated

CRYSTAL CLEAR SUD

TX0940015 Low Level
Water Type
Surface Water
PFAS Detected
2
Above MCL
0
State
Texas
Data Period
2023–2025

PFAS Test Results

CompoundDetectedvs. EPA LimitEPA LimitStatus
PFBA
Perfluorobutanoic acid
5.60pptNo federal limit—Unregulated
PFPeA
Perfluoropentanoic acid
4.00pptNo federal limit—Unregulated

CITY OF SAN MARCOS

TX1050001 Low Level
Water Type
Groundwater
PFAS Detected
4
Above MCL
0
State
Texas
Data Period
2023–2025

PFAS Test Results

CompoundDetectedvs. EPA LimitEPA LimitStatus
PFHxS
Perfluorohexane sulfonic acid
3.40ppt
34% of limit
10 pptBelow limit
lithium
11300.00pptNo federal limit—Unregulated
PFBA
Perfluorobutanoic acid
11.40pptNo federal limit—Unregulated
PFPeA
Perfluoropentanoic acid
4.20pptNo federal limit—Unregulated

TEXAS STATE UNIVERSITY - SAN MARCOS

TX1050003 Low Level
Water Type
Groundwater
PFAS Detected
1
Above MCL
0
State
Texas
Data Period
2023–2025

PFAS Test Results

CompoundDetectedvs. EPA LimitEPA LimitStatus
lithium
9500.00pptNo federal limit—Unregulated
Note: ZIP code 78666 is served by 4 separate water utilities. Results above show data for each system independently.

Data source: EPA Unregulated Contaminant Monitoring Rule, 5th cycle (UCMR 5) — January 2026 release.

UCMR 5 tested ~10,000 public water systems serving more than 25 people between 2023-2025 for 29 PFAS compounds.

Detection values represent the highest single-sample result measured at entry points to the distribution system.

View raw EPA data →