No health-based violations on EPA record since 2016.
Serves about 176,266 people (44,359 connections) with surface water bought from Stockton East Water District.
From EPA's record for CA3910001. PurityMap is independent of California Water Service.
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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 January 2025 to September 2025.
| Contaminant | Result | Limit | Status | Sampled | Source |
|---|---|---|---|---|---|
| Perfluorooctanesulfonic acid (PFOS) | 5.2 ng/L | 4.0 ng/L federal MCL (2024) | Above a historical reference; current applicability unverified | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 4,8-Dioxa-3H-perfluorononanoic acid (ADONA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals) | < 5 ng/L | 10 ng/L federal MCL (2024) | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA) | < 6 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Nonafluoro-3,6-dioxaheptanoic acid (NFDHA) | < 20 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoro-3-methoxypropanoic acid (PFMPA) | < 4 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoro-4-methoxybutanoic acid (PFMBA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| 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 | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorobutanoic acid (PFBA) | < 5 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorodecanoic acid (PFDA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorododecanoic acid (PFDoA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoroheptanesulfonic acid (PFHpS) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoroheptanoic acid (PFHpA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorohexanesulfonic acid (PFHxS) | < 3 ng/L | 10 ng/L federal MCL (2024) | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorohexanoic acid (PFHxA) | < 3 ng/L | 400,000 ng/L Michigan EGLE state MCL (strictest US state) | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorononanoic acid (PFNA) | < 4 ng/L | 10 ng/L federal MCL (2024) | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorooctanoic acid (PFOA) | < 4 ng/L | 4.0 ng/L federal MCL (2024) | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoropentanesulfonic acid (PFPeS) | < 4 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoropentanoic acid (PFPeA) | < 3 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorotetradecanoic acid (PFTA) | < 8 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluorotridecanoic acid (PFTrDA) | < 7 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
| Perfluoroundecanoic acid (PFUnA) | < 2 ng/L | No federal or state limit; shown for transparency | Not detected above the reporting limit | 2025-01-06 to 2025-09-09 | UCMR5 Analytical Results: CALIFORNIA WATER SERVICE - STOCKTON (CA3910001) |
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 →California Water Service'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, California Water Service uses surface water bought from Stockton East Water District.
No health-based violations on EPA record since 2016. The record comes from EPA's SDWIS compliance database.
Lead was not detected at the 90th percentile of tap samples in California Water Service's latest lead and copper round, which ended in December 2024. The federal action level is 15 µg/L.
PurityMap has no verified website for California Water Service. 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.