Water Quality Report · Updated October 07, 2026
ONTARIO MUNICIPAL UTILITIES COMPANY
ONTARIO MUNICIPAL UTILITIES COMPANY delivers tap water graded D (59/100) by TapWaterSafety.org. The utility serves approximately 185,010 residents in ONTARIO, California using surface water (purchased). The most significant water quality concerns are: PFAS contamination; Haloacetic acids (HAA5) significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline. For questions, the utility can be reached at 909-395-2682.
Is ONTARIO tap water safe to drink?
ONTARIO MUNICIPAL UTILITIES COMPANY delivers tap water that earns a grade of D (59/100) from TapWaterSafety.org — a below-average rating, with multiple concerns including pfas contamination.
The utility serves 185,010 residents in ONTARIO, 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), Perfluorohexane sulfonate (PFHXS), Chromium (hexavalent), Bromodichloromethane, Dibromochloromethane, Dibromoacetic acid, Nitrate and nitrite, Chloroform, Bromoform, Nitrate, Trichloroacetic acid, 1,2-Dibromo-3-chloropropane (DBCP), Perfluorooctanoic acid (PFOA), Dichloroacetic 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 ONTARIO MUNICIPAL UTILITIES COMPANY (system ID CA3610034) 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 ONTARIO residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for ONTARIO MUNICIPAL UTILITIES COMPANY.
PFAS contamination
Severe concernPerfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
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 16.4 ppb, 273x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 32.3 ppb, 215x above the EWG health guideline of 0.15 ppb.
Contact ONTARIO MUNICIPAL UTILITIES COMPANY
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 ONTARIO
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.
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 59/100 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 |
16.4 ppb | 0.06 | — | — | — | — | — | 273× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
32.3 ppb | 0.15 | 80.0 | 100 | — | — | — | 215× over |
| Perfluorohexane sulfonate (PFHXS) PFAS |
0.163 ppt | 0.001 | 10.0 | — | — | — | — | 163× over |
| Chromium (hexavalent) Heavy metal |
3.12 ppb | 0.02 | — | — | — | — | — | 156× over |
| Bromodichloromethane Disinfection byproduct |
7.45 ppb | 0.06 | — | — | — | — | — | 124× over |
| Dibromochloromethane Disinfection byproduct |
9.17 ppb | 0.1 | — | — | — | — | — | 92× over |
| Dibromoacetic acid Disinfection byproduct |
1.53 ppb | 0.03 | — | — | — | — | — | 51× over |
| Nitrate and nitrite Inorganic |
2.77 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 20× over |
| Chloroform Disinfection byproduct |
7.17 ppb | 0.4 | — | — | — | — | — | 18× over |
| Bromoform Disinfection byproduct |
8.46 ppb | 0.5 | — | — | — | — | — | 17× over |
| Nitrate Inorganic |
2.28 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 16× over |
| Trichloroacetic acid Disinfection byproduct |
1.55 ppb | 0.1 | — | — | — | — | — | 15× over |
| 1,2-Dibromo-3-chloropropane (DBCP) Other |
0.0151 ppb | 0.0017 | 0.2 | — | — | — | — | 8.9× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.482 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 5.4× over |
| Dichloroacetic acid Disinfection byproduct |
0.82 ppb | 0.2 | — | — | — | — | — | 4.1× over |
| Vanadium Other |
9.61 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Perchlorate Disinfection byproduct |
0.454 ppb | 1.0 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
87.8 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Perfluorooctane sulfonate (PFOS) PFAS |
0.072 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | Below guideline |
| 1,4-Dioxane Semi-volatile organic compound |
0.0263 ppb | 0.35 | — | — | 50 | 1 | — | Below guideline |
| Molybdenum Other |
2.92 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Bromochloromethane Other |
0.00204 ppb | 0.06 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
7.86 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Monobromoacetic acid Disinfection byproduct |
0.118 ppb | 25.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
0.234 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
0.307 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.316 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
0.163 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| 1,1-Dichloroethane Volatile organic compound |
0.000459 ppb | 3.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.099 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| 1-Butanol Other |
0.12 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.166 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.
ONTARIO MUNICIPAL UTILITIES COMPANY service area
This water system serves 1 community in San Bernardino County, California. Click any city for its dedicated tap water quality page.
Find the right filter for ONTARIO water
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