San Marcos, California Water Quality Report
Water quality data for 2 water systems serving 113,596 people.
Water Source
Detected Contaminants
| Contaminant | Detected Level | EPA Limit (MCL) | Health Guideline | % of Limit | Status |
|---|---|---|---|---|---|
| lithium | 52.0 | No federal limit | 10.0 ug/L(EPA/USGS HBSL) | 520% | Above guideline |
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Compliance & Violations
Active Violations (8)
4H
Jul 2, 2025
52
Oct 1, 2023
Violation
Unknown
Violation
Unknown
Violation
Unknown
Violation
Unknown
Violation
Unknown
Violation
Unknown
Resolved Violations (117)
03
Aug 1, 2024 — Aug 31, 2024
03
Jul 1, 2024 — Jul 31, 2024
03
Jul 1, 2024 — Sep 30, 2024
03
Apr 1, 2024 — Jun 30, 2024
03
Apr 1, 2024 — Jun 30, 2024
+ 112 more resolved violations
Frequently Asked Questions
Is San Marcos tap water safe to drink?
San Marcos's water meets all EPA maximum contaminant levels. However, 1 contaminants were detected at various levels. Some residents may prefer additional filtration for peace of mind.
What contaminants are in San Marcos tap water?
1 contaminants have been detected in San Marcos's water supply across 2 water systems. See the full contaminant table above for details.
How can I improve my water quality in San Marcos?
Install a water filter rated for the specific contaminants found in San Marcos's water. See our filter recommendations above. You can also request your utility's Consumer Confidence Report for the most current test results.
Does San Marcos have any water quality violations?
Yes, San Marcos currently has 8 active violations. See the violations section above for details.