TX / San Marcos
TX · Tap water records
San Marcos tap water, in plain English
Here is what the EPA's own data shows about tap water in San Marcos. According to EPA SDWIS data retrieved June 2026, San Marcos is served by 3 active community water systems, together reported to serve about 137,288 people.
As of June 2026, EPA records show 314 violations across the community water system(s) serving San Marcos, going back to the earliest EPA record. 97 of these are classified by the EPA as health-based (a contaminant recorded above the limit the EPA tracks); the rest are monitoring or reporting violations. Each is listed by system below, with its status.
What the EPA has on record, by system
City Of San Marcos
72,970 served · surface water · PWSID TX1050001 - Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 3 times between January 2016 and October 2025. The EPA record lists a level of 0.082 MG/L; the limit (MCL) is 0.08 MG/L. EPA records do not show all of these as returned to compliance.
- Monitoring Chlorite: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in February 2021. All have since returned to compliance, per EPA records.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between March 2014 and May 2016. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in December 2015. All have since returned to compliance, per EPA records.
Texas State University - San Marcos
43,552 served · groundwater · PWSID TX1050003 - Health-based Lead and Copper Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in April 2015. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between December 2017 and January 2018. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 7 times between December 2013 and September 2016. All have since returned to compliance, per EPA records.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 5 times between June 2010 and April 2015. All have since returned to compliance, per EPA records.
- Monitoring E. COLI: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in April 2012. All have since returned to compliance, per EPA records.
Crystal Clear Sud
20,766 served · surface water · PWSID TX0940015 - Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 6 times between January 2019 and July 2019. The EPA record lists a level of 0.094 MG/L; the limit (MCL) is 0.08 MG/L. All have since returned to compliance, per EPA records.
- Health-based Total Haloacetic Acids (HAA5): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 6 times between January 2019 and July 2019. The EPA record lists a level of 0.062 MG/L; the limit (MCL) is 0.06 MG/L. All have since returned to compliance, per EPA records.
- Health-based Long Term 2 Enhanced Surface Water Treatment Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 78 times between April 2012 and June 2015. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Health-based Surface Water Treatment Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 3 times in April 2012. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 4 times between October 2015 and December 2019. All have since returned to compliance, per EPA records.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in March 2019. All have since returned to compliance, per EPA records.
- Monitoring Aluminum: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Arsenic: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Barium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Cadmium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Chromium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Iron: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Manganese: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Mercury: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Silver: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Antimony, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Beryllium, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Thallium, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Zinc: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Selenium: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Chloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Fluoride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Sulfate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring TDS: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Endrin: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring BHC-GAMMA: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Methoxychlor: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Toxaphene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Di(2-ethylhexyl) adipate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Simazine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Di(2-ethylhexyl) phthalate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Hexachlorocyclopentadiene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Atrazine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring LASSO: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Heptachlor: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Heptachlor epoxide: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring HEXACHLOROBENZENE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Benzo(a)pyrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Pentachlorophenol: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Chlordane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,2,4-Trichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring cis-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Xylenes, Total: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring DICHLOROMETHANE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring o-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring p-Dichlorobenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Vinyl chloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,1-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring trans-1,2-Dichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,2-Dichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,1,1-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Carbon tetrachloride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,2-Dichloropropane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Trichloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring 1,1,2-Trichloroethane: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Tetrachloroethylene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring CHLOROBENZENE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Benzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Toluene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Ethylbenzene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring Styrene: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in January 2019. EPA records do not show all of these as returned to compliance.
- Monitoring E. COLI: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in August 2017. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times in July 2017. All have since returned to compliance, per EPA records.
- Monitoring Interim Enhanced Surface Water Treatment Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 74 times between April 2012 and April 2015. All have since returned to compliance, per EPA records.
What this means
A health-based violation means a contaminant was recorded above the limit the EPA tracks for it. A monitoring or reporting violation means a required test or report was late or missed — not that a contaminant was measured above a limit. “Returned to compliance” means the EPA recorded the issue as resolved.
This page summarizes the EPA's own records and does not assess whether your water is safe to drink. For the most current details, you can verify every record directly with the EPA, and contact your water system with questions.
Source: U.S. EPA Envirofacts SDWIS, retrieved June 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.