- EPA's UCMR 5 testing looked for 30 contaminants here and found 1.
Public EPA test results
What EPA records show for California Water Service - Stockton
EPA CA3910001 · serves San Joaquin County, CA · about 182,775 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
California Water Service - Stockton (EPA CA3910001)
What EPA records show for California Water Service - Stockton, as of October 14, 2026
We found no health-based violations in EPA's records for this system (CA3910001) since July 1, 2021, as of October 14, 2026.
Source: EPA ECHO record for California Water Service - Stockton (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, 2022–Dec 31, 2024). 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.
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 California Water Service - Stockton use chloramine?
We didn't find chloramine in California Water Service - Stockton's EPA treatment records. That's not a complete list; your utility's annual water quality report says which disinfectant it uses.
What EPA records show for this system
Reported results in EPA records (data as of Oct 14–15, 2026)