Water Quality Report · Updated October 07, 2026
GREAT OAKS WC INC
GREAT OAKS WC INC delivers tap water graded B (78/100) by TapWaterSafety.org. The utility serves approximately 110,088 residents in SAN JOSE, California using groundwater. The most significant water quality concerns are: Haloacetic acids (HAA5) significantly above health guideline; Chromium (hexavalent) significantly above health guideline; Arsenic significantly above health guideline. For questions, the utility can be reached at 408-227-9540.
Is SAN JOSE tap water safe to drink?
GREAT OAKS WC INC delivers tap water that earns a grade of B (78/100) from TapWaterSafety.org — a good rating, with only minor concerns relative to health-based guidelines.
The utility serves 110,088 residents in SAN JOSE, drawing from groundwater.
Public testing data identifies 12 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA5), Chromium (hexavalent), Arsenic, Dibromoacetic acid, Total trihalomethanes (TTHMs), Haloacetic acids (HAA9), Nitrate, Bromoform, Dibromochloromethane, Nitrate and nitrite, Bromodichloromethane, Chloroform. 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 GREAT OAKS WC INC (system ID CA4310022) 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 GREAT OAKS WC INC.
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.
Chromium (hexavalent) significantly above health guideline
Moderate concernChromium (hexavalent) detected at 3.77 ppb, 189x above the EWG health guideline of 0.02 ppb.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 0.225 ppb, 56x above the EWG health guideline of 0.004 ppb.
Contact GREAT OAKS WC INC
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 78/100 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 |
| Chromium (hexavalent) Heavy metal |
3.77 ppb | 0.02 | — | — | — | — | — | 189× over |
| Arsenic Heavy metal |
0.225 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 56× over |
| Dibromoacetic acid Disinfection byproduct |
1.59 ppb | 0.03 | — | — | — | — | — | 53× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
7.65 ppb | 0.15 | 80.0 | 100 | — | — | — | 51× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
3.02 ppb | 0.06 | — | — | — | — | — | 50× over |
| Nitrate Inorganic |
1.7 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 12× over |
| Bromoform Disinfection byproduct |
5.41 ppb | 0.5 | — | — | — | — | — | 11× over |
| Dibromochloromethane Disinfection byproduct |
1.07 ppb | 0.1 | — | — | — | — | — | 11× over |
| Nitrate and nitrite Inorganic |
1.56 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 11× over |
| Bromodichloromethane Disinfection byproduct |
0.2 ppb | 0.06 | — | — | — | — | — | 3.3× over |
| Chloroform Disinfection byproduct |
0.762 ppb | 0.4 | — | — | — | — | — | 1.9× over |
| Barium Heavy metal |
84.0 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Vanadium Other |
1.65 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
9.96 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
0.184 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Molybdenum Other |
0.0393 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.571 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Trichlorotrifluoroethane Other |
0.107 ppb | 4000.0 | — | — | — | — | — | Below guideline |
| 1,1,1-Trichloroethane Other |
0.104 ppb | — | 200.0 | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.178 ppb | — | — | — | — | — | — | Below guideline |
| Chromium (total) Heavy metal |
0.6 ppb | — | 100.0 | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.155 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.
GREAT OAKS WC INC service area
This water system serves 1 community in Santa Clara 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.