Is San Marcos, TX tap water safe?
Supplied by City of San Marcos · serves 72,970 people (42,746 connections) · Surface water · EPA ID TX1050001
Data: U.S. EPA · How we read the data · How we check it
Buys water from Alliance Regional Water Authority 1B. Treated water bought from another system can carry that system's contaminants.
Summary
No federal limits exceeded in EPA data.
- PFAS
- Detected, below limit3 of 29 PFAS found at least once. All averages below the federal limits.
- Lead
- Below action level1.63 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Dec 2024. Your home's pipes can make yours higher.
- Violations
- Resolved2 health-based violations since 2016, most recently Oct 2025.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Want to reduce what was found? Filters for these results.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read City of San Marcos's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (512) 393-8107. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 7 entry points tested Nov 2023 to Aug 2024. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Detected, below limit Limit 10 ppt | 1.7 ppt 17% of the limit |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Detected, below limit Limit 1 | 0.17 |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Detected, below limit Guideline 6,000 ppt | 2.85 ppt |
| PFHxA Not detected Guideline 3,000 ppt | – |
| PFPeA Detected, no limit | 2.9 ppt |
29 PFAS tested, 3 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Detected in 5 of 26 samples. Highest result 11.3 ppb. EPA's non-enforceable screening level is 10 ppb. Below screening level The screening level is how EPA decides what to study further, not a health limit. There is no federal limit for lithium and no filter is certified to remove it. About lithium.
Lead and copper
Latest 90th percentile: 1.63 ppb lead (Jan 2022 – Dec 2024). Below action level
Highest since 2016: 2.8 ppb (Dec 2017).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2022 – Dec 2024 | 1.63 ppb |
| Jan 2019 – Dec 2021 | 1.91 ppb |
| Jan 2018 – Jun 2018 | 2.1 ppb |
Earlier results (9)
| Jul 2017 – Dec 2017 | 2.8 ppb |
| Jan 2013 – Dec 2015 | 3.4 ppb |
| Jan 2010 – Dec 2012 | 3.14 ppb |
| Jan 2008 – Dec 2010 | 3.43 ppb |
| Jan 2005 – Dec 2007 | 3 ppb |
| Jan 1999 – Dec 2001 | 2.4 ppb |
| Jan 1996 – Dec 1998 | 3.7 ppb |
| Jan 1995 – Dec 1995 | 6.7 ppb |
| Jan 1994 – Dec 1994 | 4.9 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
| When | What happened |
|---|---|
| Jan 2016 – Oct 2025 2 times | The running annual average for TTHM was above the legal limit. EPA record: TTHM · Maximum Contaminant Level Violation, Average · measured 0.081 mg/l (limit 0.080 mg/L) Resolved |
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 3.5 ppb | 300 ppb |
| Chlorate | 1,100 ppb | 210 ppb |
| Vanadium | 3.1 ppb | 21 ppb |
| Strontium | 0.8 ppm | 1.5 ppm |
| Chromium-6 | 0.17 ppb | – |
| Molybdenum | 1.2 ppb | 40 ppb |
Where it serves
San Marcos
ZIP codes the system reported serving: 78666, 78667
Nearby utilities
- City of Kyle Kyle · 9 mi
- Green Valley Special Utility District New Braunfels · 16 mi
- New Braunfels Utilities New Braunfels · 16 mi
- Sjwtx Triple Peak Plant Canyon Lake · 19 mi · PFAS above limit
- City of Austin Water & Wastewater Austin · 32 mi
- City of Pflugerville Pflugerville · 44 mi · PFAS above limit
Questions
Is San Marcos tap water safe to drink?
Most of San Marcos gets its water from City of San Marcos. City of San Marcos had 2 health-based violations since 2016, all since resolved. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does San Marcos water have PFAS?
Yes. EPA's 2023–2025 testing of City of San Marcos found 3 PFAS at least once. None of the averages were above the federal limits.
What is the lead level in San Marcos water?
The most recent 90th-percentile lead result for City of San Marcos is 1.63 ppb, for the period ending Dec 2024. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for TX1050001: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID TX1050001).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask City of San Marcos at (512) 393-8107, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.