San Marcos
TX

Is San Marcos, TX Tap Water Safe to Drink?

San Marcos tap water meets federal Safe Drinking Water Act standards but 2 of 3 ZIP codes show detections above EPA health guidelines, primarily for 6:2 FTS. A certified filter is recommended for households that want an additional layer of protection.

5Water systems
3ZIP codes
66.7%ZIPs above EPA guideline
Metro areaAustin-Round Rock-San Marcos, TX
Latest data2025-10-07

Where Does San Marcos Get Its Water?

Water in San Marcos, TX is provided by 5 public water systems: CITY OF SAN MARCOS, TEXAS STATE UNIVERSITY - SAN MARCOS, COUNTY LINE SUD, CRYSTAL CLEAR SUD and MAXWELL WSC.

How Is San Marcos Tap Water Treated?

Treated water is disinfected using chloramines and free chlorine and on-site generated disinfectant. Treatment includes air stripping, conventional treatment (coagulation, flocculation, and filtration), direct filtration, groundwater disinfection and membrane filtration.

What's in San Marcos Tap Water?

The following contaminants were detected most frequently in San Marcos public water systems. 2 of 3 ZIP codes showed detections above EPA health guidelines.

ContaminantPeak detectedEPA guidelineZIPs detectedStatus
6:2 FTS 0.005 µg/L 0.005 µg/L 1 ZIP Above guideline
11Cl-PF3OUdS 0.005 µg/L 0.005 µg/L 1 ZIP Above guideline
lithium 9.8 µg/L — 1 ZIP Within guideline
PFTrDA 0.007 µg/L — 0 ZIPs Within guideline
8:2 FTS 0.005 µg/L — 0 ZIPs Within guideline

Health Risk Profile for San Marcos

Based on EPA monitoring data, 2 of 3 ZIP codes in San Marcos have recorded detections above EPA health guidelines. Sensitive populations such as infants, pregnant individuals, and those with weakened immune systems may benefit from an additional layer of protection such as a certified point-of-use filter.

Best Broad-Spectrum Filters for This Water Profile

This city profile includes PFAS detections, chlorine disinfection, and other dissolved contaminants. Reverse osmosis (RO) systems certified under NSF/ANSI 58 provide broad reduction coverage; for PFAS specifically, confirm NSF/ANSI P473 or equivalent PFAS reduction certification.

Waterdrop G3P600 Reverse Osmosis System
Under-sink RO system

8-stage tankless RO system certified to NSF/ANSI 58, reduces 1,000+ contaminants including PFAS, lead, arsenic, fluoride, and nitrates.

See recommendations matched to your exact address: choose your ZIP code below.

Frequently Asked Questions about San Marcos Tap Water

Is San Marcos tap water safe to drink?

San Marcos tap water meets Safe Drinking Water Act requirements but 2 of 3 ZIP codes show contaminant levels above EPA health-based guidelines. A certified point-of-use filter adds an extra layer of protection.

What contaminants are in San Marcos tap water?

The most commonly detected contaminants in San Marcos water systems include: 6:2 FTS, 11Cl-PF3OUdS, lithium. See the ZIP-level reports for exact measurements and EPA guideline comparisons.

Where does San Marcos get its drinking water?

San Marcos receives water from 5 public water systems, including CITY OF SAN MARCOS.

Do I need a water filter in San Marcos?

If your ZIP code is among those with detections above EPA health guidelines, choose a filter certified for the specific contaminants shown in your ZIP report. Reverse osmosis is generally the broadest option for PFAS, lithium, and many other dissolved contaminants.

How often is San Marcos tap water tested?

Public water systems in San Marcos are required by the EPA to test for regulated contaminants on schedules ranging from daily (for microbials and disinfectants) to annual or triennial (for many chemical contaminants). Results are published in annual Consumer Confidence Reports (CCRs). The data on this page reflects the most recent available EPA monitoring results, with the latest sample date of 2025-10-07.

Tap water reports by ZIP in San Marcos

Water utilities serving San Marcos, TX

Service area boundaries are approximate and based on state filings or modeled estimates. Contact your utility to confirm exact service at a specific address.

Modeled boundaries are shown with a dashed outline.

Also covers / overlaps with