Drinking water quality · 2024
What's in Ontario, CA tap water
42 contaminants were measured in the Ontario, CA water system's 2024 annual report. Each is shown below against its federal limit.
- Reporting year
- 2024
- Contaminants measured
- 42
- Over federal limit
- 0
- Approaching the limit
- 1
- Service area
- CA
state-level CCR
Approaching the limit (≥ 80%)
PFAS — EPA UCMR5 (2023–2025)
2 PFAS compounds above EPA limits in Ontario, CA
The EPA finalized the first-ever federal drinking-water limits for six PFAS compounds in April 2024. These numbers come straight from EPA's UCMR5 lab dataset — every U.S. system serving more than 3,300 people tested every PFAS sample at an entry point to its distribution system. PFAS not listed below were either tested and not detected, or not yet sampled.
PFOA (Perfluorooctanoic acid)
● Over EPA limit (7.5×)Measured 30 ng/LEPA limit 4 ng/LSample year 2023Samples 1 detect / 35
PFOS (Perfluorooctane sulfonic acid)
● Over EPA limit (1.3×)Measured 5.2 ng/LEPA limit 4 ng/LSample year 2023Samples 1 detect / 35
PFHxS (Perfluorohexane sulfonic acid)
● Below limitMeasured 4.2 ng/LEPA limit 10 ng/LSample year 2023Samples 1 detect / 35
PFPeA
● Detected (no federal limit)Measured 6.7 ng/LSample year 2023Samples 2 detect / 35
PFHxA
● Detected (no federal limit)Measured 7.1 ng/LSample year 2023Samples 1 detect / 35
PFBA
● Detected (no federal limit)Measured 6.4 ng/LSample year 2023Samples 2 detect / 35
PWSID CA3610034 · Source: EPA UCMR5. Limits per EPA's April 2024 PFAS National Primary Drinking Water Regulation. PFAS values reported in nanograms per liter (ng/L) — note that 1 ng/L = 1 part per trillion.
Where your water comes from · EPA SDWIS
Ontario, CA's drinking water comes from ground water, drawn from 18 sources.
Source
18ground water
- WELL · 14
- WELL NO. · 3
- WELL 41 - RAW
Treatment
18treatment plants
- WELL 43 - TREATED (CL2)
- WELL 37 AND 39 IX FINISHED BLEND EFF
- WELLS 37 AND 39 IX COMBINED VESSEL EFF
- + 15 more
Distribution
0storage units
Also buys water from CHINO BASIN DESALTER AUTH. - DESALTER 2, JURUPA COMMUNITY SD, and 3 more.
Source: EPA SDWIS facilities inventory. Methodology.
Compliance history
Federal Safe Drinking Water Act violation & enforcement records (EPA SDWIS). A violation is a regulatory determination by the state or EPA — separate from the measured levels above.
- Treatment technique violationHealth-based1 violation on record · most recent Jun 1993resolved
Source: EPA SDWIS / ECHO. View the full federal record on EPA ECHO ↗
Other
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Diquat | 18 ug/LReported levelSource water | None set | Approaching the limit |
| Nitrate Nitrite | 2.7 mg/LReported levelLocal Groundwater | 10 mg/LMCL | Within the limit |
| Chlorine Total | 0.98 mg/LReported levelOMUC's Entire Distribution System | 4 mg/LMCL | Within the limit |
Physical & aggregate
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| TurbidityA measure of cloudiness from suspended particles in the water. | 0.73 NTUReported levelOMUC's Entire Distribution System | 1 NTUMCL | Within the limit |
+By source (2)— OMUC's Entire Distribution System, Local Groundwater
| |||
| AlkalinityA measure of the water's capacity to neutralize acids. | 156 mg/LReported levelLocal Groundwater | None set | Detected — no federal limit |
+By source (4)— Local Groundwater, Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| Bicarbonate | 156 mg/LReported levelLocal Groundwater | None set | Detected — no federal limit |
| HardnessA measure of dissolved calcium and magnesium minerals. | 200 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| OdorA measure of detectable smell in the water. | 0.5Reported levelSource water | None set | Detected — no federal limit |
| pHA measure of how acidic or basic the water is. | 7.9Reported levelLocal Groundwater | None set | Detected — no federal limit |
+By source (2)— Local Groundwater, OMUC's Entire Distribution System
| |||
| Specific ConductanceA measure of how well water conducts electricity, which tracks dissolved mineral content. | 508Reported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| TOCTotal organic carbon — a measure of organic material dissolved in the water. | 2.3 mg/LReported levelSource water | None set | Detected — no federal limit |
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 372 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
Inorganic chemicals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| NitrateA compound from fertilizer runoff, septic systems, and erosion of natural deposits. | 6.7 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | 10 mg/LMCL | Within the limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone), Purchased Groundwater CDA 1 (870 Zone) +1 more
| |||
| FluorideA mineral often added to drinking water to help prevent tooth decay. | 0.16 mg/LReported levelLocal Groundwater | 4 mg/LMCL | Within the limit |
| ChlorideA naturally occurring salt compound. | 98 mg/LReported levelPurchased Groundwater CDA 1 (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| SulfateA naturally occurring mineral from rock and soil. | 34 mg/LReported levelSource water | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Local Groundwater, Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
Disinfection byproducts
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| TTHMTotal trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter. | 50 ug/LReported levelOMUC's Entire Distribution System | None set | Within the limit |
| HAA5Haloacetic acids — a group of five disinfection byproducts formed when disinfectants react with organic matter. | 13 ug/LReported levelOMUC's Entire Distribution System | None set | Within the limit |
| PerchlorateA chemical used in rocket fuel and fireworks that can also form during disinfection. | 1.5 ug/LReported levelLocal Groundwater | None set | Detected — no federal limit |
+By source (4)— Local Groundwater, Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
VOCs & pesticides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| TrichloroethyleneAn industrial solvent (TCE) used in metal degreasing. | 0.78 ug/LReported levelLocal Groundwater | 5 ug/LMCL | Within the limit |
| DBCP1,2-dibromo-3-chloropropane — a banned soil fumigant pesticide. | 0.27 ng/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Within the limit |
Radionuclides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Gross AlphaGross alpha particle activity — a combined measure of alpha-emitting radioactive substances. | 2.3 pCi/LReported levelPurchased Groundwater JCSD (870 Zone) | 15 pCi/LMCL | Within the limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Local Groundwater, Purchased Groundwater CDA 1 (870 Zone)
| |||
| UraniumA naturally occurring radioactive metal from erosion of natural deposits. | 0.63 pCi/LReported levelPurchased Groundwater JCSD (870 Zone) | 20 pCi/LMCL | Detected — no federal limit |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| CopperA metal that enters water from corroding household plumbing. | 130 ug/L90th percentileOMUC's Entire Distribution System | 1300 ug/LAction level | Within the limit |
| SeleniumA trace element from natural deposits and industrial discharge. | 4.2 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Within the limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone)
| |||
| ArsenicA naturally occurring element that also enters water from industry and agriculture. | 0.57 ug/LReported levelPurchased Groundwater CDA 1 (870 Zone) | None set | Within the limit |
| BariumA metal from erosion of natural deposits and industrial discharge. | 80 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | 2000 ug/LMCL | Within the limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone), Purchased Groundwater CDA 1 (870 Zone)
| |||
| LeadA toxic metal that leaches into water from old service lines, solder, and plumbing fixtures. | 0.0006 mg/L90th percentileAt the tap | 0.015 mg/LAction level | Within the limit |
| AluminumA common element sometimes used as a treatment coagulant. | 41 ug/LReported levelSource water | None set | Detected — no federal limit |
| CalciumA naturally occurring mineral that contributes to water hardness. | 65 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 2.2 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone), Purchased Groundwater CDA 1 (870 Zone)
| |||
| MagnesiumA naturally occurring mineral that contributes to water hardness. | 9.4 mg/LReported levelSource water | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| PotassiumA naturally occurring mineral from rock and soil. | 2.4 mg/LReported levelSource water | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater JCSD (870 Zone), Local Groundwater, Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| SilicaA naturally occurring compound from sand and rock. | 21 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (2)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone)
| |||
| SodiumA naturally occurring salt component. | 32 mg/LReported levelPurchased Groundwater CDA 1 (870 Zone) | None set | Detected — no federal limit |
+By source (4)— Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
| Vanadium | 3.8 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (2)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone)
| |||
Source: Ontario, CA's 2024 Consumer Confidence Report — the annual drinking-water report every U.S. utility is required to publish. The numbers on this page are the utility's own. A water-quality report covers an entire service area, not a single address.
People also ask about Ontario, CA's water
+Is Ontario, CA tap water safe to drink in 2024?
Every one of the 42 contaminants measured in Ontario, CA's 2024 Consumer Confidence Report is below its federal limit. "Safe" under the EPA's drinking-water standards is health-based, not aesthetic — but by those standards, no measured contaminant in this report exceeds its enforceable threshold. Individual health concerns (e.g. immunocompromised, infant, pregnancy) may warrant additional filtering regardless of compliance.
+What contaminants are in Ontario, CA tap water?
42 contaminants were measured in Ontario, CA's 2024 Consumer Confidence Report, spanning metals, physical & aggregate, and pfas ("forever chemicals"). 11 have an enforceable federal limit; the rest are detected but unregulated. Every measured value, in the utility's own units, is on this page.
+Are any contaminants in Ontario, CA tap water approaching the federal limit?
One contaminant is between 80% and 100% of the federal limit in this report: Diquat. Approaching means measured but not in violation — a margin that can close quickly if conditions change.
+Where does the data on this page come from?
Every value is transcribed from Ontario, CA's 2024 Consumer Confidence Report — the annual drinking-water report every U.S. public water utility is required by federal law to publish. The original source document is archived and viewable on this site. A water-quality report covers an entire service area, not a single address.
+How often is Ontario, CA's water quality data updated?
Each U.S. public water utility publishes one Consumer Confidence Report per year, covering the prior calendar year's measurements. This page reflects the 2024 report; a new report will replace it once the utility publishes its next annual update.
More water systems in CA
Upland, City of — Upland, CaMonte Vista WdSan Antonio Water CompanyThree Valleys MWD — Claremont, CaSierra Water Resources - Sierra CitySonora Water Resources, IncOwens Valley Water Resources, Inc.Rancho CucamongaCucamonga Valley Water DistrictCalifornian Mobile Home ParkWagon Train Road LlcMono Vista Ranch MhpPomona - City, Water Dept.Calif State Polytechnical Univ - PomonaCalifornia Institution for MenChino, City ofChino Hills, City ofDesert View Trailer ParkMWD - Eagle MountainMWD of So Cal Iron MountainLa Verne, City WdMWD of So Cal Gene PlantGoose Creek Golf ClubGswc-south San Gabriel — San Dimas, CaAll water systems →