Water Quality in San Marcos, TX: 2 Violations — Grade B
Grade B · Score 83/100 · 5 water systems · Updated 2026-05-03
San Marcos's water is mostly safe. Minor violations exist but are primarily monitoring-related.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
San Marcos, TX has 2 violations in the EPA compliance history — breakdown below.
Water Quality by ZIP Code in San Marcos
Water quality varies across San Marcos's 2 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 78666 | B | 80 | 1 | 0 | View report → |
| 78667 | A | 85 | 1 | 0 | View report → |
Water Quality Overview
San Marcos, Texas receives a water quality grade of B with an overall score of 83 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 5 water systems serving San Marcos have accumulated 2 EPA violations (all monitoring/reporting type). These violations are tracked across 2 ZIP codes serving approximately 137,288 people.
What Grade B Means
A grade of B indicates good compliance with EPA drinking water standards. While not perfect, San Marcos's water systems meet the vast majority of federal requirements. Minor violations may exist but typically relate to monitoring or reporting rather than health-based standards.
Lead Levels
The average 90th percentile lead level across San Marcos water systems is 0.0016 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
Water Systems Serving San Marcos
San Marcos is served by 5 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 137,288 people across 2 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
The EPA has taken 8 enforcement actions against water systems serving San Marcos. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in San Marcos
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
EPA Enforcement History
The EPA and state regulators have taken 4 enforcement actions against water systems serving San Marcos. Recent actions:
| Date | Action Type |
|---|---|
| 2022-05-09 | State Informal Action |
| 2021-05-18 | State Informal Action |
| 2021-05-18 | State Informal Enforcement |
| 2021-05-18 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2022-05-09.
San Marcos vs. Nearby Texas Cities
How San Marcos's water quality compares to similar cities in Texas:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| San Marcos | B | 2 | 5 | 137,288 |
| Abilene | A | 170 | 5 | 137,705 |
| Carrollton | A | 0 | 1 | 136,170 |
| Beaumont | B | 210 | 5 | 135,882 |
Common Questions About San Marcos Water
These are the most common questions residents search for about water quality in San Marcos, Texas:
Is San Marcos water hard or soft? Water hardness varies by source. San Marcos's 5 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink San Marcos tap water? San Marcos's water receives a grade of B (83/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for San Marcos? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
San Marcos vs. Texas Average
Understanding how San Marcos compares to the broader Texas average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within San Marcos.
ZIP Codes in San Marcos
San Marcos spans 2 ZIP codes. The ZIP with the lowest water quality score is 78666. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.
Frequently Asked Questions
Your Water is Safe — Here's How to Keep It That Way
Grade B is excellent news. Here's what proactive homeowners do to maintain water quality:
Annual Water Testing
EPA recommends annual testing even with clean water. Home test kits: $20-$50. Catches changes before they become problems.
Maintenance Filtration
A basic carbon filter removes chlorine taste and catches emerging contaminants like PFAS that aren't yet fully regulated.
Plumbing Check
Even safe city water picks up lead from home pipes. If your home was built before 1986, a one-time pipe inspection is recommended.