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Updated 2026-10-15
County water report

Santa Clara County Water Quality: 11 Cities Ranked by the Records

Santa Clara County, California: 11 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.

Find my systemOpen on the mapPrivate wells in Santa Clara County
Across the county's systems

Highest result for each contaminant

One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.

LithiumDetected in 5 systems of 11 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest25.5 µg/L
Perfluorooctanoic acid (PFOA)Detected in 1 system of 11 tested4.0 ng/L federal MCL (2024) · US EPAHighest8 ng/L
  • CITY OF GILROY8 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF CUPERTINONot detected · below 4.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MORGAN HILLNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-07-31 to 2024-12-03
  • CITY OF MOUNTAIN VIEWNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 4.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 4.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 4.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • SAN JOSE WATERNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-02-16 to 2025-02-11
  • STANFORD UNIVERSITYNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
Perfluorooctanesulfonic acid (PFOS)Detected in 2 systems of 11 tested4.0 ng/L federal MCL (2024) · US EPAHighest6.2 ng/L
  • SAN JOSE WATER6.2 ng/LSample date: 2023-02-16 to 2025-02-11
  • CITY OF GILROY5.8 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF CUPERTINONot detected · below 4.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MORGAN HILLNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-07-31 to 2024-12-03
  • CITY OF MOUNTAIN VIEWNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 4.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 4.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 4.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • STANFORD UNIVERSITYNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
Perfluorohexanesulfonic acid (PFHxS)Detected in 4 systems of 11 tested10 ng/L federal MCL (2024) · US EPAHighest5.5 ng/L
  • SAN JOSE WATER5.5 ng/LSample date: 2023-02-16 to 2025-02-11
  • CITY OF GILROY3.5 ng/LSample date: 2024-12-17 to 2025-06-25
  • CWSC LOS ALTOS SUBURBAN3.5 ng/LSample date: 2023-06-06 to 2025-03-25
  • CITY OF MORGAN HILL3.3 ng/LSample date: 2023-07-31 to 2024-12-03
  • CITY OF CUPERTINONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MOUNTAIN VIEWNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • STANFORD UNIVERSITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
Lead (90th percentile)Detected in 4 systems of 11 tested15 µg/L federal action level · US EPAHighest2.7 µg/L
Perfluorobutanesulfonic acid (PFBS)Detected in 1 system of 11 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest9.4 ng/L
  • CITY OF GILROY9.4 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF CUPERTINONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MORGAN HILLNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-07-31 to 2024-12-03
  • CITY OF MOUNTAIN VIEWNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • SAN JOSE WATERNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-16 to 2025-02-11
  • STANFORD UNIVERSITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
Perfluorohexanoic acid (PFHxA)Detected in 2 systems of 11 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest7 ng/L
  • CITY OF GILROY7 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF MORGAN HILL3.4 ng/LSample date: 2023-07-31 to 2024-12-03
  • CITY OF CUPERTINONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MOUNTAIN VIEWNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • SAN JOSE WATERNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-16 to 2025-02-11
  • STANFORD UNIVERSITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 11 testedNo federal or state limit; shown for transparencyHighest3.6 ng/L
  • CITY OF GILROY3.6 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF CUPERTINONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MORGAN HILLNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-07-31 to 2024-12-03
  • CITY OF MOUNTAIN VIEWNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • SAN JOSE WATERNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-16 to 2025-02-11
  • STANFORD UNIVERSITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
1 more contaminant detectedShow
Perfluoropentanoic acid (PFPeA)Detected in 2 systems of 11 testedNo federal or state limit; shown for transparencyHighest7.8 ng/L
  • CITY OF GILROY7.8 ng/LSample date: 2024-12-17 to 2025-06-25
  • CITY OF MORGAN HILL3.5 ng/LSample date: 2023-07-31 to 2024-12-03
  • CITY OF CUPERTINONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-24 to 2023-11-20
  • CITY OF MILPITASNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-16 to 2025-06-24
  • CITY OF MOUNTAIN VIEWNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-03-08 to 2023-12-06
  • CITY OF PALO ALTONot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-05 to 2024-06-18
  • CITY OF SANTA CLARANot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-01 to 2025-12-15
  • CITY OF SUNNYVALENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-10 to 2025-01-22
  • CWSC LOS ALTOS SUBURBANNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-06-06 to 2025-03-25
  • SAN JOSE WATERNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-16 to 2025-02-11
  • STANFORD UNIVERSITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-11-20 to 2025-08-20
22 PFAS tested, none detected in any systemShow

Tested in these 11 systems: CITY OF CUPERTINO, CITY OF GILROY, CITY OF MILPITAS, CITY OF MORGAN HILL, CITY OF MOUNTAIN VIEW, CITY OF PALO ALTO, CITY OF SANTA CLARA, CITY OF SUNNYVALE, CWSC LOS ALTOS SUBURBAN, SAN JOSE WATER, STANFORD UNIVERSITY

  • 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
  • 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
  • 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
  • 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
  • N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
  • N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
  • Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
  • Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
  • Perfluoro-3-methoxypropanoic acid (PFMPA)
  • Perfluoro-4-methoxybutanoic acid (PFMBA)
  • Perfluorobutanoic acid (PFBA)
  • Perfluorodecanoic acid (PFDA)
  • Perfluorododecanoic acid (PFDoA)
  • Perfluoroheptanesulfonic acid (PFHpS)
  • Perfluorononanoic acid (PFNA)
  • Perfluoropentanesulfonic acid (PFPeS)
  • Perfluorotetradecanoic acid (PFTA)
  • Perfluorotridecanoic acid (PFTrDA)
  • Perfluoroundecanoic acid (PFUnA)
11 cities

Cities ranked by the records

Showing 6 of 11 cities · scores are system-level, not tap tests

Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.

PFAS in Santa Clara County2 of 11 city reports had a PFAS sample above a 2024 EPA limit
  1. Campbell6.2 ng/L
  2. Gilroy5.8 ng/L
4.0 ng/L federal MCL · PFOS, ng/LPFAS in California
Lead

0of 11 cities above the 15 µg/L action level

Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.

Lead in California
Who supplies the county

Largest water systems

  1. CampbellSAN JOSE WATER · CA4310011
    1,039,920 served
  2. SunnyvaleCITY OF SUNNYVALE · CA4310014
    157,566 served
  3. Santa ClaraCITY OF SANTA CLARA · CA4310012
    134,587 served
  4. MilpitasCITY OF MILPITAS · CA4310005
    81,915 served
  5. Mountain ViewCITY OF MOUNTAIN VIEW · CA4310007
    81,340 served
  6. Palo AltoCITY OF PALO ALTO · CA4310009
    67,658 served
  7. Los AltosCWSC LOS ALTOS SUBURBAN · CA4310001
    63,559 served
  8. GilroyCITY OF GILROY · CA4310004
    59,426 served
  9. Morgan HillCITY OF MORGAN HILL · CA4310006
    47,374 served
  10. StanfordSTANFORD UNIVERSITY · CA4310013
    23,817 served
Questions

Frequently asked

How does Santa Clara County tap water compare across cities?

PurityMap ranks 11 cities in Santa Clara County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Sunnyvale's main water system: CITY OF SUNNYVALE · PWSID CA4310014 · Purity Score 100 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.

How many Santa Clara County cities had a PFAS sample above a 2024 EPA limit?

2 of 11 Santa Clara County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Gilroy (PFOA 8 ng/L), Campbell (PFOS 6.2 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 4.

Is there lead in Santa Clara County tap water?

Utilities report lead as a 90th-percentile result from home taps. 4 of 11 Santa Clara County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.

Have Santa Clara County water systems had drinking-water violations?

1 city in Santa Clara County has a health-based violation in the federal SDWIS record within about the last ten years. Each city report lists the contaminant, year and whether it was resolved.

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