EPA CA4310022 · serves Santa Clara County, CA · about 112,582 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
Great Oaks WC Inc (EPA CA4310022)
What EPA records show for Great Oaks WC Inc, as of October 14, 2026
We found no health-based violations in EPA's records for this system (CA4310022) since July 1, 2021, 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, 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 5.
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 Great Oaks WC Inc use chloramine?
We didn't find chloramine in Great Oaks WC Inc's EPA treatment records. That's not a complete list; your utility's annual water quality report says which disinfectant it uses.
Reported results in EPA records (data as of Oct 14–15, 2026)
EPA's UCMR 5 testing looked for 30 contaminants here and found 5.
Lithium: found in 34 of 38 samples, average 11.2 µg/L, highest 16 µg/L (EPA UCMR 5 testing, Jun 2025–Dec 2025)
PFHxS (a PFAS): found in 5 of 38 samples, average 0.80 ppt, highest 8 ppt (EPA UCMR 5 testing, Jun 2025–Dec 2025)
PFPeA (a PFAS): found in 5 of 38 samples, average 0.50 ppt, highest 4.7 ppt (EPA UCMR 5 testing, Jun 2025–Dec 2025)
PFHxA (a PFAS): found in 5 of 38 samples, average 0.50 ppt, highest 4.5 ppt (EPA UCMR 5 testing, Jun 2025–Dec 2025)
PFOS (a PFAS): found in 1 of 38 samples, average 0.10 ppt, highest 4.6 ppt (EPA UCMR 5 testing, Jun 2025–Dec 2025)
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, 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.
Source: EPA SDWIS (ECHO SDWA bulk download), data as of Oct 14, 2026
Source: EPA UCMR 5 occurrence data, data as of Oct 15, 2026
These are EPA's public records for this water system, shown as of October 14, 2026. If you represent this utility, or think a record here is wrong, tell us: Report an error. If the error is in EPA's own records, your state drinking water program can correct it there, and this page updates at our next data refresh.
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