San Luis Obispo Water Quality
California
According to EPA SDWIS, San Luis Obispo, California is served by 20 community water systems covering about 69,727 people. The same extract lists 37 health-based violation records, most recently coded 1040 in 2025. Counts are historical EPA registry rows, not a current compliance or drinkability score.
Drinking water in San Luis Obispo, California is delivered through 20 EPA-regulated community water systems serving an estimated 69,727 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 37 violation records across the 20 active community systems shown here. Monitoring and reporting records are not present in the extract. The records carry 4 distinct EPA contaminant codes: Nitrate, Revised Total Coliform Rule, LEAD AND COPPER RULE REVISIONS, Stage 1 Disinfectants and Disinfection Byproducts Rule. 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 |
|---|---|---|---|
| SAN LUIS OBISPO WATER DEPARTMENT | 47,788 | 0 | Clean |
| CALIFORNIA MENS COLONY | 15,000 | 1 | Health |
| LOPEZ PROJECT | 1,569 | 2 | Health |
| SLO CWWD NO. 23 - SANTA MARGARITA | 1,291 | 0 | Clean |
| SLOCSA #10A - CAYUCOS | 1,200 | 0 | Clean |
| SLO CSA NO. 16 - SHANDON | 1,085 | 0 | Clean |
| LAUREATE WATER COMPANY | 700 | 0 | Clean |
| SANTA YSABEL RANCH MWC | 344 | 0 | Clean |
| IRISH HILLS MUTUAL WATER CO | 135 | 0 | Clean |
| CALLENDER GROVE MUTUAL WATER | 126 | 0 | Clean |
| LAS VENTANAS RANCH | 108 | 0 | Clean |
| AFUERA DE CHORRO WATER COMPANY | 85 | 0 | Clean |
| BARON CANYON MUTUAL WATER CO. | 81 | 0 | Clean |
| AVILA VALLEY MUTUAL WATER CO | 75 | 0 | Clean |
| MONTE SERENO MUTUAL BENEFIT WATER | 65 | 0 | Clean |
| BEAR VALLEY WATER COMPANY | 45 | 0 | Clean |
| HIGUERA APARTMENTS | 30 | 34 | Health |
| SLO CSA NO. 10 - CAYUCOS WTP | 0 | 0 | Clean |
| CHORRO VALLEY PIPELINE - SLO COUNTY | 0 | 0 | Clean |
| NACIMIENTO WATER PROJECT | 0 | 0 | Clean |
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 |
|---|---|---|
| HIGUERA APARTMENTS | Nitrate | 2025-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2025-07-01 |
| LOPEZ PROJECT | Revised Total Coliform Rule | 2025-04-01 |
| LOPEZ PROJECT | Revised Total Coliform Rule | 2025-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2025-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2025-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2025-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2025-01-01 |
| HIGUERA APARTMENTS | LEAD AND COPPER RULE REVISIONS | 2024-10-17 |
| HIGUERA APARTMENTS | Nitrate | 2024-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2024-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2023-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-04-01 |
| HIGUERA APARTMENTS | Nitrate | 2022-01-01 |
| HIGUERA APARTMENTS | Nitrate | 2021-10-01 |
| HIGUERA APARTMENTS | Nitrate | 2021-07-01 |
| HIGUERA APARTMENTS | Nitrate | 2021-04-05 |
| HIGUERA APARTMENTS | Nitrate | 2017-01-01 |
| CALIFORNIA MENS COLONY | Stage 1 Disinfectants and Disinfection Byproducts Rule | 2012-08-03 |
What are San Luis Obispo's health-based records for?
San Luis Obispo's health-based violation records carry 4 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.
| Contaminant | Records | Systems |
|---|---|---|
| Nitrate | 33 | 1 |
| Revised Total Coliform Rule | 2 | 1 |
| Stage 1 Disinfectants and Disinfection Byproducts Rule | 1 | 1 |
| Lead and Copper Rule Revisions | 1 | 1 |
TRI Facilities in San Luis Obispo
| Facility | Total Releases |
|---|---|
| U.S. Army National Guard Camp San Luis Obispo Ranges | 31.9K lbs |
| Promega Corp | 10.1K lbs |
| Entegris - San Luis Obispo | 2.0K lbs |
| Martin Marietta Ca Ready Mix - San Luis Obipso | 0 lbs |
| Calportland Co San Luis Obispo | 0 lbs |
Frequently Asked Questions
What does EPA SDWIS list for drinking water in San Luis Obispo, California? ▼
How many water violations does San Luis Obispo have in this EPA extract? ▼
What contaminants were found in San Luis Obispo water? ▼
How many water systems serve San Luis Obispo? ▼
Where does San Luis Obispo get its drinking water? ▼
Are there pollution sources near San Luis Obispo? ▼
How does San Luis Obispo compare in California?
Of the 909 California places with at least one community water system on file, San Luis Obispo ranks #14 by number of systems (20).
Either side of it: Hollister (21), Red Bluff (20), Apple Valley (19), Lancaster (19)
About This Data
Figures here are the current EPA SDWIS extract joined to the 20 community water systems whose service area lists San Luis Obispo, 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.