- EPA's UCMR 5 testing looked for 30 contaminants here and found 1.
- Lithium: found in 1 of 4 samples, average 2.5 µg/L, highest 10 µg/L (EPA UCMR 5 testing, Jun 2023–Mar 2024)
- Lead, 90th percentile: 0 ppb at the latest result in EPA records for a monitoring period that ran on or after July 1, 2021, at or below EPA's 15 ppb action level (EPA SDWIS, monitoring period Jan 1, 2023–Dec 31, 2025). The 90th percentile is a system-wide measure from homes sampled under EPA's lead rule; it isn't a result for your home.
Public EPA test results
San Luis Obispo, CA tap water: what EPA records show
EPA CA4010009 · serves San Luis Obispo County, CA · about 49,534 people (EPA SDWIS)
This report shows EPA's federal records for this water system: UCMR 5 testing, lead testing and violations. It isn't a test of the water at your tap, and it has no Water Score.
Public EPA test results
San Luis Obispo Water Department (EPA CA4010009)
EPA data as of October 14, 2026. For San Luis Obispo's main utility, San Luis Obispo Water Department: We found no health-based violations in EPA's records for this system (CA4010009) since July 1, 2021, as of October 14, 2026. PFOA and PFOS were not detected at or above EPA's reporting level in EPA's UCMR 5 testing.
What EPA records show for San Luis Obispo Water Department, as of October 14, 2026
We found no health-based violations in EPA's records for this system (CA4010009) since July 1, 2021, as of October 14, 2026.
Source: EPA ECHO record for San Luis Obispo Water Department (SDWIS). Data as of October 14, 2026.
Lead, 90th percentile: 0 ppb at the latest result in EPA records for a monitoring period that ran on or after July 1, 2021, at or below EPA's 15 ppb action level (EPA SDWIS, monitoring period Jan 1, 2023–Dec 31, 2025). The 90th percentile is a system-wide measure from homes sampled under EPA's lead rule; it isn't a result for your home.
EPA's UCMR 5 testing looked for 30 contaminants here and found 1.
PFOA and PFOS were not detected at or above EPA's reporting level in EPA's UCMR 5 testing.
Source: EPA records (SDWIS, UCMR 5). SDWIS: data as of Oct 14, 2026. EPA UCMR 5 data, samples through June 2026.
Your water bill names your utility.
Does San Luis Obispo Water Department use chloramine?
We didn't find chloramine in San Luis Obispo Water Department's EPA treatment records. That's not a complete list; your utility's annual water quality report says which disinfectant it uses.