- EPA's UCMR 5 testing looked for 30 contaminants here and found 2.
- Lithium: found in 4 of 8 samples, average 20.4 µg/L, highest 57 µg/L (EPA UCMR 5 testing, Oct 2023–Jul 2024)
- PFBA (a PFAS): found in 1 of 8 samples, average 0.70 ppt, highest 5.6 ppt (EPA UCMR 5 testing, Oct 2023–Jul 2024)
- Lead, 90th percentile: 0.59 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, 2024–Dec 31, 2026). 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
South San Gabriel, CA tap water: what EPA records show
EPA CA1910223 · serves Los Angeles County, CA · about 26,451 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
Gswc-South San Gabriel (EPA CA1910223)
EPA data as of October 14, 2026. For South San Gabriel's main utility, Gswc-South San Gabriel: We found no health-based violations in EPA's records for this system (CA1910223) 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 Gswc-South San Gabriel, as of October 14, 2026
We found no health-based violations in EPA's records for this system (CA1910223) since July 1, 2021, as of October 14, 2026.
Source: EPA ECHO record for Gswc-South San Gabriel (SDWIS). Data as of October 14, 2026.
Lead, 90th percentile: 0.59 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, 2024–Dec 31, 2026). 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 2.
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 Gswc-South San Gabriel use chloramine?
We didn't find chloramine in Gswc-South San Gabriel's EPA treatment records. That's not a complete list; your utility's annual water quality report says which disinfectant it uses.