Water Quality Report · Updated October 07, 2026
CALIFORNIA WATER SERVICE - STOCKTON
CALIFORNIA WATER SERVICE - STOCKTON delivers tap water graded F (49/100) by TapWaterSafety.org. The utility serves approximately 176,266 residents in SAN JOSE, California using surface water (purchased). The most significant water quality concerns are: PFAS contamination; Arsenic significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline. For questions, the utility can be reached at 408-367-8593.
Is SAN JOSE tap water safe to drink?
CALIFORNIA WATER SERVICE - STOCKTON delivers tap water that earns a grade of F (49/100) from TapWaterSafety.org — a poor rating, with significant contamination concerns and/or recent violations.
The utility serves 176,266 residents in SAN JOSE, drawing from surface water (purchased).
Public testing data identifies 15 contaminants in this water above EWG's health-based guidelines, including: Arsenic, Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Perfluorohexane sulfonate (PFHXS), Haloacetic acids (HAA9), Chloroform, Trichloroacetic acid, Bromodichloromethane, Chromium (hexavalent), Dichloroacetic acid, Nitrate and nitrite, Nitrate, Dibromochloromethane, Perfluorooctane sulfonate (PFOS), Uranium. For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
EPA compliance record
Official U.S. EPA records for CALIFORNIA WATER SERVICE - STOCKTON (system ID CA3910001) for the last 3 years. Checked 2026-10-07.
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Quick actions for SAN JOSE residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for CALIFORNIA WATER SERVICE - STOCKTON.
PFAS contamination
Severe concernPerfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 1.71 ppb, 427x above the EWG health guideline of 0.004 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 55.2 ppb, 368x above the EWG health guideline of 0.15 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 36.2 ppb, 362x above the EWG health guideline of 0.1 ppb.
Contact CALIFORNIA WATER SERVICE - STOCKTON
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Treatment Plant
Recommended water filters for SAN JOSE
Filters matched to the specific contaminants in this water supply.
Filter certified for PFOA/PFOS (NSF/ANSI 53 or 58)
$180-$750Reverse osmosis and some carbon block filters reduce PFAS. Look for certification to NSF/ANSI 53 or 58 for PFOA/PFOS.
Reverse osmosis certified for arsenic (NSF/ANSI 58)
$429-$599Reverse osmosis certified under NSF/ANSI 58 for arsenic is the most reliable home option.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts like TTHM. Look for NSF/ANSI 53 VOC or chloroform reduction.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
Score breakdown
This utility's overall score of 49/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Arsenic Heavy metal |
1.71 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 427× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
55.2 ppb | 0.15 | 80.0 | 100 | — | — | — | 368× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Perfluorohexane sulfonate (PFHXS) PFAS |
0.253 ppt | 0.001 | 10.0 | — | — | — | — | 253× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
14.6 ppb | 0.06 | — | — | — | — | — | 243× over |
| Chloroform Disinfection byproduct |
49.1 ppb | 0.4 | — | — | — | — | — | 123× over |
| Trichloroacetic acid Disinfection byproduct |
11.0 ppb | 0.1 | — | — | — | — | — | 110× over |
| Bromodichloromethane Disinfection byproduct |
5.75 ppb | 0.06 | — | — | — | — | — | 96× over |
| Chromium (hexavalent) Heavy metal |
1.76 ppb | 0.02 | — | — | — | — | — | 88× over |
| Dichloroacetic acid Disinfection byproduct |
8.36 ppb | 0.2 | — | — | — | — | — | 42× over |
| Nitrate and nitrite Inorganic |
1.66 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 12× over |
| Nitrate Inorganic |
1.45 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 10× over |
| Dibromochloromethane Disinfection byproduct |
0.531 ppb | 0.1 | — | — | — | — | — | 5.3× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
1.45 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 4.8× over |
| Uranium Radiological |
0.81 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 1.9× over |
| Vanadium Other |
9.06 ppb | 21.0 | — | — | — | — | — | Below guideline |
| 1,2,3-Trichloropropane* Other |
0.000271 ppb | 0.0007 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
74.5 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Perfluorooctanoic acid (PFOA) PFAS |
0.013 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | Below guideline |
| Barium Heavy metal |
70.9 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Bromoform Disinfection byproduct |
0.0333 ppb | 0.5 | — | — | — | — | — | Below guideline |
| 1,4-Dioxane Semi-volatile organic compound |
0.0168 ppb | 0.35 | — | — | 50 | 1 | — | Below guideline |
| Trichloroethylene Volatile organic compound |
0.0185 ppb | 0.4 | 5.0 | 10 | 20 | 1.7 | — | Below guideline |
| Manganese Heavy metal |
4.05 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Aluminum Heavy metal |
7.27 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Molybdenum Other |
0.341 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.204 ppb | 53.0 | — | — | — | — | — | Below guideline |
| 1,1-Dichloroethane Volatile organic compound |
0.000589 ppb | 3.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.249 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
0.062 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.025 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
0.042 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Chromium (total) Heavy metal |
1.63 ppb | — | 100.0 | — | — | — | — | Below guideline |
| Dichlorodifluoromethane Other |
0.305 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.0136 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Germanium Other |
0.256 ppb | — | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
CALIFORNIA WATER SERVICE - STOCKTON service area
This water system serves 1 community in San Joaquin County, California. Click any city for its dedicated tap water quality page.
Find the right filter for SAN JOSE water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.