San Marcos Tap Water Quality Report
San Marcos's water has 4 contaminants above EPA MCLGs. We recommend using a certified water filter.
Other systems listed for San Marcos with results above guidelines: TEXAS STATE UNIVERSITY - SAN MARCOS (2 above guidelines), BLUE AGAVE MOBILE HOME PARK (1 above guidelines), LEISUREWOODS WATER (2 above guidelines), MAXWELL SUD (3 above guidelines), MEADOW WOODS WATER SUPPLY (3 above guidelines), SOUTH BUDA WCID 1 (3 above guidelines), CRYSTAL CLEAR SUD (4 above guidelines)
People Served
67,468
Health-based violations since 2020
1
CITY OF SAN MARCOS. EPA SDWA violation data as of Q2 2026 (downloaded 2026-07-09).
Latest sample on file
Feb 2025 · CITY OF SAN MARCOS
Utilities publish newer results in their annual water quality report (Consumer Confidence Report).
Is San Marcos Tap Water Safe to Drink?
We strongly recommend using a certified water filter to reduce exposure: San Marcos's water has 4 contaminants above EPA health-based guidelines. Check our filter recommendations below for NSF-certified options that can remove the specific contaminants found in San Marcos's water.
CITY OF SAN MARCOS, San Marcos's water system, serves 67,468 people. 9 other systems are listed for San Marcos. Each system's results are listed under its own name, never added to CITY OF SAN MARCOS's. Water quality testing is conducted regularly and reported to the EPA. The latest sample on file for CITY OF SAN MARCOS is from Feb 2025.
Boil water advisories are issued by water systems and state agencies, and they change from day to day. Boil water advisories in Texas
San Marcos Water Service Areas
What these numbers actually mean for San Marcos, TX
We read San Marcos, TX’s published record and send you a short report — which findings warrant a decision, which to ignore, and what to do about it. Including when the answer is nothing.
- 4 contaminants above EPA MCLGs and 6 contaminants with an EPA health goal detected in some samples (no level on file)
- 233 results on file
- 23 PFAS compounds on record
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Recommended Water Filters for San Marcos
Based on San Marcos's water quality data, these NSF-certified filters are recommended to remove contaminants above EPA MCLGs.
Solventum Purification Inc.
3MRO401
NSF Certified:
Daily Production
11.48 gpd
Highlights:
- NSF-58 certified reverse osmosis system
- 11.48 GPD production capacity
- Reduces total dissolved solids (TDS) for purer water
Removes 15 contaminants:
+10 more
Copper, Cryptosporidium, Fluoride, Lead, Radium 226, Radium 228, Radium, combined (-226 & -228), Selenium, Total Dissolved Solids, Turbidity
Solventum Purification Inc.
3MRO301
NSF Certified:
Daily Production
11.48 gpd
Highlights:
- NSF-58 certified reverse osmosis system
- 11.48 GPD production capacity
- Reduces total dissolved solids (TDS) for purer water
Removes 15 contaminants:
+10 more
Copper, Cryptosporidium, Fluoride, Lead, Radium 226, Radium 228, Radium, combined (-226 & -228), Selenium, Total Dissolved Solids, Turbidity
Culligan
ZeroWater
NSF Certified:
Flow Rate
1.9 gpm
Daily Production
1 gpd
Highlights:
- Compact design
- Easy to set up
- Affordable
- NSF-42, NSF-53, NSF-401 certified
Removes 19 contaminants:
+14 more
Strontium, Molybdenum, Fluoride, Uranium, Lead, Total PFAS, Chlorine, 25, Phosphorus, Bicarbonate, Calcium, Carbonate, Magnesium, Sodium
Santevia
Bath Filter
NSF Certified:
Flow Rate
0.36 gpm
Highlights:
- Organic cotton design reduces plastic used in construction
- Affordable upfront & ongoing cost
- The only bath filter that removed 100% chlorine with “normal” faster faucet flow
Removes 1 contaminants:
Verify Your Water Quality with Independent Testing
With 4 contaminants above EPA MCLGs and 6 contaminants with an EPA health goal detected in some samples (no level on file), independent laboratory testing provides a second opinion and can track changes over time.
SimpleLab
Advanced Home Water Test
$269
Comprehensive water analysis testing over 200 contaminants including bacteria, heavy metals, and chemical compounds.
Tap Score
Haloacetic Acids (HAA9) Test
$275
Tests for disinfection byproducts formed when chlorine reacts with organic matter in water treatment.
Tap Score
Advanced Microplastics Test
$829
Cutting-edge testing for microplastics particles in drinking water using advanced laboratory techniques.
With 4 contaminants above health guidelines, you may want to explore water purification options. Learn how to make distilled water at home for applications like humidifiers, CPAP machines, and baby formula.
What San Marcos's water readings can explain
Utility-reported data for San Marcos includes sulfate and a chlorine-based disinfectant — the readings behind these common tap water questions. We publish a city-level hardness figure for San Marcos, resolved from its water systems where they report one and estimated from county sampling where they do not. Each page starts with the hot-tap and cold-tap check, then shows what your own water system reported.
On a private well near San Marcos? Public-water results do not apply to private wells. See Hays County well water testing and USGS risk data — modeled arsenic, nitrate, and the tests to run.
Water softener cost and installation in San Marcos
San Marcos's tap water measures 11.5 grains per gallon (196.0 mg/L) — very hard on the USGS scale, the range where scale on fixtures and appliances is the usual complaint.
Water softener cost for 11.5 gpg water in San Marcos — equipment and local installation labour for your ZIP code, with the sizing arithmetic shown in full. For the national picture first, read what a water softener costs — equipment, installation labour and ten-year ownership, each separated out. For Texas as a whole, read water softener cost in Texas — priced against the plumber wage published for the state.
Frequently Asked Questions About San Marcos Tap Water
San Marcos's water has 4 contaminants above EPA MCLGs. We strongly recommend using a certified water filter to reduce exposure to these contaminants. Check our filter recommendations below for NSF-certified options that can remove the specific contaminants found in San Marcos's water.
Spotted something off on this page?
Residents keep our data honest.
This form corrects our data; it does not reach CITY OF SAN MARCOS. For a problem with your water now (discolored water, no water, low pressure, a leak), contact CITY OF SAN MARCOS directly.
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