Water Quality Report · Updated October 07, 2026
CALIFORNIA WATER SERVICE-S SAN FRANCISCO
CALIFORNIA WATER SERVICE-S SAN FRANCISCO delivers tap water graded C (65/100) by TapWaterSafety.org. The utility serves approximately 64,146 residents in SAN JOSE, California using surface water (purchased). The most significant water quality concerns are: Arsenic significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline; Haloacetic acids (HAA9) 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-S SAN FRANCISCO delivers tap water that earns a grade of C (65/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 64,146 residents in SAN JOSE, drawing from surface water (purchased).
Public testing data identifies 14 contaminants in this water above EWG's health-based guidelines, including: Arsenic, Haloacetic acids (HAA5), Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Trichloroacetic acid, Chloroform, Dichloroacetic acid, Bromodichloromethane, Chromium (hexavalent), Nitrate and nitrite*, Dibromochloromethane, Nitrate, Bromate*, Dibromoacetic acid. 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-S SAN FRANCISCO (system ID CA4110009) 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-S SAN FRANCISCO.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 2.15 ppb, 538x above the EWG health guideline of 0.004 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.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 20.1 ppb, 335x above the EWG health guideline of 0.06 ppb.
Contact CALIFORNIA WATER SERVICE-S SAN FRANCISCO
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.
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. Look for NSF/ANSI 53 VOC 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 65/100 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 |
2.15 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 538× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
20.1 ppb | 0.06 | — | — | — | — | — | 335× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
34.4 ppb | 0.15 | 80.0 | 100 | — | — | — | 229× over |
| Trichloroacetic acid Disinfection byproduct |
8.27 ppb | 0.1 | — | — | — | — | — | 83× over |
| Chloroform Disinfection byproduct |
30.8 ppb | 0.4 | — | — | — | — | — | 77× over |
| Dichloroacetic acid Disinfection byproduct |
14.4 ppb | 0.2 | — | — | — | — | — | 72× over |
| Bromodichloromethane Disinfection byproduct |
2.79 ppb | 0.06 | — | — | — | — | — | 47× over |
| Chromium (hexavalent) Heavy metal |
0.582 ppb | 0.02 | — | — | — | — | — | 29× over |
| Nitrate and nitrite* Inorganic |
2.95 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 21× over |
| Dibromochloromethane Disinfection byproduct |
0.894 ppb | 0.1 | — | — | — | — | — | 8.9× over |
| Nitrate Inorganic |
1.07 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 7.7× over |
| Bromate* Disinfection byproduct |
0.4 ppb | 0.1 | 10.0 | 10 | 10 | 0.1 | — | 4.0× over |
| Dibromoacetic acid Disinfection byproduct |
0.119 ppb | 0.03 | — | — | — | — | — | 4.0× over |
| Chlorate Disinfection byproduct |
135.4 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Perchlorate* Disinfection byproduct |
0.332 ppb | 1.0 | — | — | — | — | — | Below guideline |
| Uranium Radiological |
0.12 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | Below guideline |
| Bromoform Disinfection byproduct |
0.0819 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
74.7 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Manganese Heavy metal |
5.89 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Vanadium Other |
0.767 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Aluminum* Heavy metal |
9.16 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.0931 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.154 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Bromide* Other |
9.28 ppb | — | — | — | — | — | — | Below guideline |
| Chromium (total)* Heavy metal |
3.03 ppb | — | 100.0 | — | — | — | — | Below guideline |
| Fluoride* Inorganic |
0.272 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Lithium Other |
9.0 ppb | — | — | — | — | — | — | Below guideline |
| Quinoline Other |
0.00275 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-S SAN FRANCISCO service area
This water system serves 1 community in San Mateo 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.