Water Quality: San Luis Obispo, CA
22 water systems • 69,851 people served
Multiple Health ViolationsWater Quality Summary
San Luis Obispo is served by 22 public water systems with a combined service population of 69,851 people, and has 103 EPA Safe Drinking Water Act violations on record. Critically, 35 of those are health-based violations, meaning one or more contaminants were detected above EPA-established safe levels — a serious public health concern. San Luis Obispo's violation count is 115% above the national average for California. Contaminants associated with violations include Chlorine, E. coli, Selenium, Stage 2 DBP.
Contaminants Found
Eye and nose irritation at high levels; long-term exposure above the MCL may cause liver and kidney damage.
Common source: Water treatment disinfectant added to kill harmful microorganisms
EPA limit: 4.0 mg/L (MRDL — Maximum Residual Disinfectant Level)
Causes gastrointestinal illness; certain strains (e.g., O157:H7) can cause severe kidney failure and death.
Common source: Fecal contamination from humans or animals entering the water supply
EPA limit: Zero (no E. coli permitted in drinking water)
Hair loss, nail brittleness, and nervous system damage at elevated concentrations.
Common source: Natural geological deposits, mining discharges, oil refinery waste
EPA limit: 0.05 mg/L (50 ppb)
Trihalomethanes and haloacetic acids that increase cancer risk and may cause adverse reproductive outcomes.
Common source: Chlorine disinfection reacting with natural organic matter in source water
EPA limit: TTHM: 0.080 mg/L; HAA5: 0.060 mg/L
Water Systems Serving San Luis Obispo
| System Name | PWSID | Source | Population | Violations |
|---|---|---|---|---|
| SAN LUIS OBISPO WATER DEPARTMENT | CA4010009 | Surface Water | 47,788 | 0 |
| CALIFORNIA MENS COLONY | CA4010830 | Surface Water | 15,000 | 3 |
| LOPEZ PROJECT | CA4010022 | Surface Water | 1,569 | 2 |
| SLO CWWD NO. 23 - SANTA MARGARITA | CA4010024 | Groundwater | 1,291 | 1 |
| SLOCSA #10A - CAYUCOS | CA4010901 | Surface Water | 1,200 | 0 |
| SLO CSA NO. 16 - SHANDON | CA4010028 | Surface Water | 1,085 | 0 |
| LAUREATE WATER COMPANY | CA4000206 | Groundwater | 700 | 9 |
| SANTA YSABEL RANCH MWC | CA4000802 | Groundwater | 275 | 3 |
| GRAN CIELO MUTUAL WATER COMPANY | CA4000853 | Groundwater | 139 | 0 |
| IRISH HILLS MUTUAL WATER CO | CA4000203 | Groundwater | 135 | 10 |
| CALLENDER GROVE MUTUAL WATER | CA4000805 | Groundwater | 126 | 2 |
| LAS VENTANAS RANCH | CA4000815 | Groundwater | 108 | 0 |
| BARON CANYON MUTUAL WATER CO. | CA4000214 | Groundwater | 81 | 13 |
| AFUERA DE CHORRO WATER COMPANY | CA4000744 | Groundwater | 79 | 3 |
| AVILA VALLEY MUTUAL WATER CO | CA4000716 | Surface Water | 75 | 3 |
| MONTE SERENO MUTUAL BENEFIT WATER | CA4000808 | Groundwater | 65 | 0 |
| ANZA VINEYARD ESTATES MUTUAL WATER CO | CA4000834 | Groundwater | 60 | 0 |
| BEAR VALLEY WATER COMPANY | CA4000660 | Groundwater | 45 | 9 |
| HIGUERA APARTMENTS | CA4000563 | Groundwater | 30 | 44 |
| SLO CWD NO. 10 - CAYUCOS WTP | CA4010025 | Surface Water | 0 | 1 |
| CHORRO VALLEY PIPELINE - SLO COUNTY | CA4010030 | Surface Water | 0 | 0 |
| NACIMIENTO WATER PROJECT | CA4010080 | Surface Water | 0 | 0 |
Concerned About Your Water?
A home water filter can remove common contaminants. NSF-certified filters are tested against EPA standards.
Consider a reverse osmosis system for comprehensive filtration or a carbon filter for basic improvement.
Other Cities in California
Data Sources
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). Data includes all recorded violations for active community water systems.