No health-based violations on EPA record since 2016.
Serves about 69,973 people (18,530 connections) with surface water bought from Purissima Hills Water District and Santa Clara Valley Water District.
From EPA's record for CA4310001. PurityMap is independent of CWSC Los Altos Suburban.
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No health-based violations in the last 10 years, from EPA's SDWIS compliance database.
EPA required this system to test for 30 unregulated and emerging contaminants, from June 2023 to March 2025.
| Contaminant | Result | Limit | Status | Sampled | Source |
|---|---|---|---|---|---|
| Perfluorohexanesulfonic acid (PFHxS) | 3.5 ng/L | 10 ng/L federal MCL (2024) | Within a historical reference; current applicability unverified | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 4,8-Dioxa-3H-perfluorononanoic acid (ADONA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS) | < 2 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals) | < 5 ng/L | 10 ng/L federal MCL (2024) | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Lithium | < 9 µg/L | 10 µg/L EPA health reference level (screening, not a legal limit)Screening level, not a legal limit | Not detected above the reporting limit | 2023-06-06 to 2025-02-05 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-02-05 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA) | < 6 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-02-05 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Nonafluoro-3,6-dioxaheptanoic acid (NFDHA) | < 20 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoro-3-methoxypropanoic acid (PFMPA) | < 4 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoro-4-methoxybutanoic acid (PFMBA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorobutanesulfonic acid (PFBS) | < 3 ng/L | 2,000 ng/L EPA health advisory (screening, not a legal limit)Screening level, not a legal limit | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorobutanoic acid (PFBA) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorodecanoic acid (PFDA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorododecanoic acid (PFDoA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoroheptanesulfonic acid (PFHpS) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoroheptanoic acid (PFHpA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorohexanoic acid (PFHxA) | < 3 ng/L | 400,000 ng/L Michigan EGLE state MCL (strictest US state) | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorononanoic acid (PFNA) | < 4 ng/L | 10 ng/L federal MCL (2024) | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorooctanesulfonic acid (PFOS) | < 4 ng/L | 4.0 ng/L federal MCL (2024) | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorooctanoic acid (PFOA) | < 4 ng/L | 4.0 ng/L federal MCL (2024) | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoropentanesulfonic acid (PFPeS) | < 4 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoropentanoic acid (PFPeA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorotetradecanoic acid (PFTA) | < 8 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-02-05 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluorotridecanoic acid (PFTrDA) | < 7 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-02-05 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
| Perfluoroundecanoic acid (PFUnA) | < 2 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2023-06-06 to 2025-03-25 | UCMR5 Analytical Results: CWSC LOS ALTOS SUBURBAN (CA4310001) |
Screening tells you if something is worth a closer look; a lab result is the number you can act on.
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Screening: quick check, not lab-grade
Safe Home (EnviroTestKits)
Lead, read as one of three ranges: 0–4, 5–15 or 15+ ppb
Turnaround: 5 minutes
What it can't tell you: It shows a lead range, not an exact level, and tests nothing else unless you pay extra for the optional lab test.
Lab-certified results
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
Environmental Testing and Research Laboratories (ETR Labs), Leominster, MA · ISO/IEC 17025:2017, ANAB certificate AT-2638 · 2–4 business days after the lab receives it
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Get PurityMap updates about this water system.
Follow this water →CWSC Los Altos Suburban's phone number on EPA record is 408-367-8593. Its mailing address is 1720 NORTH FIRST STREET, SAN JOSE, CA 95112.
According to EPA's record, CWSC Los Altos Suburban uses surface water bought from Purissima Hills Water District and Santa Clara Valley Water District.
No health-based violations on EPA record since 2016. The record comes from EPA's SDWIS compliance database.
The 90th-percentile lead result in CWSC Los Altos Suburban's latest lead and copper round, which ended in December 2025, was 1.5 µg/L, below the federal action level of 15 µg/L.
PurityMap has no verified website for CWSC Los Altos Suburban. Its phone number on EPA record is 408-367-8593. Its mailing address on EPA record is 1720 NORTH FIRST STREET, SAN JOSE, CA 95112. Your water bill lists the ways to contact your supplier and pay. PurityMap does not take payments.