San Marcos Water Quality
California
According to EPA SDWIS, San Marcos, California is served by 2 community water systems covering about 113,596 people. The same extract lists 53 health-based violation records, most recently coded 1025 in 2023. Counts are historical EPA registry rows, not a current compliance or drinkability score.
Drinking water in San Marcos, California is delivered through 2 EPA-regulated community water systems serving an estimated 113,596 people. Each system is tracked in the EPA Safe Drinking Water Information System (SDWIS) under the Safe Drinking Water Act, which requires testing for regulated contaminants, consumer notification of violations, and publication of an annual Consumer Confidence Report.
PlainEnviro's health-based SDWIS extract shows 53 violation records across the 2 active community systems shown here. Monitoring and reporting records are not present in the extract. The records carry 2 distinct EPA contaminant codes: Fluoride, Nitrate. 5 TRI-reporting industrial facilities are also located within the city limits.
A past EPA health-based registry row does not describe water delivered today or current compliance status; utilities notify customers and remediate under state primacy oversight when required. For current water-quality status and treatment practices, review your local utility's most recent Consumer Confidence Report or contact the California drinking water program. All records above reflect federal EPA SDWIS data and are not independently verified against state databases.
Community Water Systems
| System Name | Pop. Served | Violations | Status |
|---|---|---|---|
| VALLECITOS WD | 113,500 | 0 | Clean |
| OCOTILLO OASIS, LLC | 96 | 53 | Health |
Does this city have health-based water violations?
These health-based records can represent Maximum Contaminant Level (MCL), Treatment Technique (TT), or Maximum Residual Disinfectant Level (MRDL) categories. A historical record does not establish that water is currently unsafe.
| Water system | Contaminant | Begin Date |
|---|---|---|
| OCOTILLO OASIS, LLC | Fluoride | 2023-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2023-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2023-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2023-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2021-01-01 |
| OCOTILLO OASIS, LLC | Nitrate | 2019-09-03 |
| OCOTILLO OASIS, LLC | Nitrate | 2019-09-03 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2017-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2016-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2015-01-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-10-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-07-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-04-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-03-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2014-03-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2013-11-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2013-11-01 |
| OCOTILLO OASIS, LLC | Fluoride | 2013-09-01 |
What are San Marcos's health-based records for?
San Marcos's health-based violation records carry 2 distinct EPA codes: some name a substance, others the drinking-water rule that was breached. Counts are records on file in the EPA SDWIS extract, not current test results.
TRI Facilities in San Marcos
| Facility | Total Releases |
|---|---|
| Sumitomo Electric Interconnect Products Inc | 393.7K lbs |
| Piercan USA Inc. | 11.1K lbs |
| Hughes Circuits Inc | 43 lbs |
| Hocking International Laboratories LLC | 0 lbs |
| Hollandia Dairy Inc | 0 lbs |
Frequently Asked Questions
What does EPA SDWIS list for drinking water in San Marcos, California? ▼
How many water violations does San Marcos have in this EPA extract? ▼
What contaminants were found in San Marcos water? ▼
How many water systems serve San Marcos? ▼
Where does San Marcos get its drinking water? ▼
Are there pollution sources near San Marcos? ▼
How does San Marcos compare in California?
Of the 909 California places with at least one community water system on file, San Marcos ranks #466 by number of systems (2).
Either side of it: Riverbank (2) , Running Springs (2) , San Ramon (2) , Santa Ana (2)
About This Data
Figures here are the current EPA SDWIS extract joined to the 2 community water systems whose service area lists San Marcos, ranked against the 909 California places with at least one system on file. Data current as of 2026-08-25.
Water system data comes from the EPA's Safe Drinking Water Information System (SDWIS). PlainEnviro's violation fetch is restricted upstream to records EPA flags as health-based and then joined to active community water systems. Monitoring and reporting violations are not included.
A health-based violation row in this extract is a historical EPA registry entry. It does not describe water delivered today or current compliance status. Many records are later resolved, and public water systems notify customers when required. For current conditions, contact your local water utility or the state drinking water program.
TRI facility data comes from the EPA Toxic Release Inventory. Facilities shown are those that self-report to the TRI program. PlainEnviro presents this data without advocacy framing.
Read our methodology - how this data is sourced, computed, and verified.