- EPA's UCMR 5 testing looked for 30 contaminants here and found 1.
- PFHxS (a PFAS): found in 2 of 36 samples, average 0.20 ppt, highest 3.5 ppt (EPA UCMR 5 testing, Jun 2023–Mar 2025)
- Lead, 90th percentile: 1.5 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
Can you drink Los Altos tap water? What EPA records show
EPA CA4310001 · serves Santa Clara County, CA · about 63,559 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
CWSC Los Altos Suburban (EPA CA4310001)
EPA data as of October 14, 2026. For Los Altos's main utility, CWSC Los Altos Suburban: We found no health-based violations in EPA's records for this system (CA4310001) 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 CWSC Los Altos Suburban, as of October 14, 2026
We found no health-based violations in EPA's records for this system (CA4310001) since July 1, 2021, as of October 14, 2026.
Source: EPA ECHO record for CWSC Los Altos Suburban (SDWIS). Data as of October 14, 2026.
Lead, 90th percentile: 1.5 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 CWSC Los Altos Suburban use chloramine?
EPA treatment records (state-reported) list chloramines for CWSC Los Altos Suburban. EPA record