What was found in San Marcos's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate-Nitrite | 2172 µg/L 22% of the EPA limit 10000 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2015 | 2/3 | SYR4 |
| Nitrate | 1990.4999999999998 µg/L 20% of the EPA limit 10000 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019
Highest in the city: 2010 µg/L — TEXAS STATE UNIVERSITY - SAN MARCOS · 43,552 people · 2019 | 2/3 | SYR4 |
| Copper | 250.49999999999983 µg/L 19% of the EPA limit 1300 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2018
Highest in the city: 1700 µg/L — TEXAS STATE UNIVERSITY - SAN MARCOS · 43,552 people · 2019 | 2/3 | SYR4 |
| Fluoride | 765 µg/L 19% of the EPA limit 4000 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Chlorite | 604 µg/L 60% of the EPA limit 1000 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| TTHM | 88.075 µg/L 110% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Barium | 46.76 µg/L 2.3% of the EPA limit 2000 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Total Haloacetic Acids (HAA5) | 35.025 µg/L 58% of the EPA limit 60 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Chloroform | 27.58499999999998 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Bromodichloromethane | 26.279999999999998 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Dibromochloromethane | 23.95499999999999 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Dichloroacetic Acid | 16.94999999999999 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Monochloroacetic Acid | 12.319999999999993 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Lithium | 11.3 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2024 | 2/3 | UCMR-5 |
| Cyanide | 10 µg/L 5% of the EPA limit 200 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Bromoform | 8.6 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Trichloroacetic Acid | 8.6 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Dibromoacetic Acid | 6.369999999999998 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 2/3 | SYR4 |
| Lead | 4.2 µg/L 28% of the EPA limit 15 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2018
Highest in the city: 4.369999999999999 µg/L — TEXAS STATE UNIVERSITY - SAN MARCOS · 43,552 people · 2019 | 2/3 | SYR4 |
| Selenium | 4.1 µg/L 8.2% of the EPA limit 50 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Arsenic | 2.2 µg/L 22% of the EPA limit 10 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Monobromoacetic Acid | 2.164999999999999 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Chromium | 1.9595 µg/L 2% of the EPA limit 100 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Combined Radium (-226 And -228) | 1.5 pCi/L 30% of the EPA limit 5 pCi/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2017 | 1/3 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 0.8700 µg/L 14% of the EPA limit 6 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Antimony, Total | 0.2220 µg/L 3.7% of the EPA limit 6 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Atrazine | 0.1600 µg/L 5.3% of the EPA limit 3 µg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2019 | 1/3 | SYR4 |
| Pfba | 0.0114 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2024 | 1/3 | UCMR-5 |
| Pfpea | 0.0042 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2024 | 1/3 | UCMR-5 |
| PFHXS | 0.0034 µg/L No EPA limit set Main supplier: CITY OF SAN MARCOS · 72,970 people · 2024 | 1/3 | UCMR-5 |
| Lead | 0.0016 mg/L 11% of the EPA limit 0.0150 mg/L Main supplier: CITY OF SAN MARCOS · 72,970 people · 2024 | 2/3 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving San Marcos
| Supplier | Population served |
|---|---|
| CITY OF SAN MARCOS | 72,970 |
| TEXAS STATE UNIVERSITY - SAN MARCOS | 43,552 |
| ALLIANCE REGIONAL WATER AUTHORITY | 0 |
Frequently asked questions about San Marcos tap water
Is San Marcos tap water safe to drink?
EPA testing detected 31 contaminants in the water serving San Marcos. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve San Marcos?
3 public water suppliers report drinking-water monitoring for San Marcos, Texas to the EPA. Each is listed above with its population served.
What contaminants are in San Marcos's water?
The contaminants EPA monitoring detected in San Marcos include Nitrate-Nitrite, Nitrate, Copper, Fluoride, Chlorite. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.