Water Quality Report · Updated October 07, 2026
CALIFORNIA WATER SERVICE CO. - HERM/REDO
CALIFORNIA WATER SERVICE CO. - HERM/REDO delivers tap water graded C (66/100) by TapWaterSafety.org. The utility serves approximately 96,853 residents in SAN JOSE, California using surface water (purchased). The most significant water quality concerns are: Haloacetic acids (HAA5) significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline; Arsenic detected. For questions, the utility can be reached at 408-367-8593.
Is SAN JOSE tap water safe to drink?
CALIFORNIA WATER SERVICE CO. - HERM/REDO delivers tap water that earns a grade of C (66/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 96,853 residents in SAN JOSE, drawing from surface water (purchased).
Public testing data identifies 16 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA5), Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Arsenic, Bromodichloromethane, Dibromochloromethane, Dibromoacetic acid, Bromochloroacetic acid, Dichloroacetic acid, Chloroform, Bromoform, Trichloroacetic acid, Uranium, Nitrate*, Nitrate and nitrite*, Chromium (hexavalent). 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 CO. - HERM/REDO (system ID CA1910134) 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 CO. - HERM/REDO.
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 14.9 ppb, 249x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 31.8 ppb, 212x above the EWG health guideline of 0.15 ppb.
Arsenic detected
Moderate concernArsenic detected at 0.72 ppb.
Contact CALIFORNIA WATER SERVICE CO. - HERM/REDO
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.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Reverse osmosis certified for arsenic (NSF/ANSI 58)
$429-$599Reverse osmosis certified under NSF/ANSI 58 for arsenic is the most reliable home option.
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 66/100 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 |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
14.9 ppb | 0.06 | — | — | — | — | — | 249× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
31.8 ppb | 0.15 | 80.0 | 100 | — | — | — | 212× over |
| Arsenic Heavy metal |
0.72 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 180× over |
| Bromodichloromethane Disinfection byproduct |
7.8 ppb | 0.06 | — | — | — | — | — | 130× over |
| Dibromochloromethane Disinfection byproduct |
10.5 ppb | 0.1 | — | — | — | — | — | 105× over |
| Dibromoacetic acid Disinfection byproduct |
2.74 ppb | 0.03 | — | — | — | — | — | 91× over |
| Bromochloroacetic acid Disinfection byproduct |
1.48 ppb | 0.02 | — | — | — | — | — | 74× over |
| Dichloroacetic acid Disinfection byproduct |
3.54 ppb | 0.2 | — | — | — | — | — | 18× over |
| Chloroform Disinfection byproduct |
6.84 ppb | 0.4 | — | — | — | — | — | 17× over |
| Bromoform Disinfection byproduct |
6.67 ppb | 0.5 | — | — | — | — | — | 13× over |
| Trichloroacetic acid Disinfection byproduct |
1.33 ppb | 0.1 | — | — | — | — | — | 13× over |
| Uranium Radiological |
5.24 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 12× over |
| Nitrate* Inorganic |
0.281 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.0× over |
| Nitrate and nitrite* Inorganic |
0.287 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.0× over |
| Chromium (hexavalent) Heavy metal |
0.0334 ppb | 0.02 | — | — | — | — | — | 1.7× over |
| Radium, combined (-226 and -228) Radiological |
0.04 pCi/L | 0.05 | 5.0 | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
126.3 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
195.0 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Selenium Heavy metal |
6.04 ppb | 30.0 | 50.0 | 20 | 40 | 30 | — | Below guideline |
| Aluminum* Heavy metal |
77.5 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Molybdenum Other |
4.9 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Vanadium Other |
1.94 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
6.39 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Monobromoacetic acid Disinfection byproduct |
0.0323 ppb | 25.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
1.17 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.0825 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.632 ppm | — | 4.0 | 1.5 | 1.5 | — | — | 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 CO. - HERM/REDO service area
This water system serves 1 community in Los Angeles 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.