San Luis Obispo Tap Water Quality: Is It Safe to Drink? (2026 Report)

San Luis Obispo, California tap water receives a grade of A (93/100), which is considered excellent. Out of 77 contaminants tested, 1 exceed EPA maximum contaminant levels (MCLs) and 2 exceed health guidelines (MCLGs). While the water meets federal standards, some residents may still choose to use a filter for additional peace of mind.

Of the 77 contaminants tested in San Luis Obispo's water supply, the most notable include Copper (90th percentile), chlorate. 1 contaminant(s) exceed EPA legal limits (MCLs). 2 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.

Yes, San Luis Obispo has 8 EPA violation(s) on record, with the most recent in 2025. Violation types include MCL, MR, MON. 4 of these are health-based violations, which are the most serious category.

Based on EPA data, using a water filter in San Luis Obispo is recommended. 1 contaminant(s) exceed legal limits. An NSF-certified filter — such as a reverse osmosis or activated carbon system — can effectively reduce many common contaminants. Choose a filter certified to remove the specific contaminants found in your area.

San Luis Obispo's drinking water is sourced from surface water and supplied by SAN LUIS OBISPO WATER DEPARTMENT and 5 other water system(s). The system serves approximately 67,933 people. Surface water sources include rivers, lakes, and reservoirs.

Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. San Luis Obispo's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.

San Luis Obispo's water quality score of 93/100 earns a grade of A, which is considered excellent. This places San Luis Obispo among the better-performing water systems in California. Visit our California state page to see how all cities in the state compare.

If you have concerns about San Luis Obispo's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (SAN LUIS OBISPO WATER DEPARTMENT) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.