Drinking water quality · 2024
· Verified
What's in Ontario, CA tap water
40 contaminants were measured in the Ontario, CA water system's 2024 annual report. Each is shown below against its federal limit — 7 sit at or above that limit.
- Reporting year
- 2024
- Contaminants measured
- 40
- Over federal limit
- 7
- Approaching the limit
- 0
- Worst contaminant
- Specific Conductance
- Service area
- CA
508.0× the limit
state-level CCR
At or above the federal limit
- Specific ConductancePhysical & aggregate · Reported level508limit 1 · 508.0× the limit
- Total Dissolved SolidsPhysical & aggregate · Reported level372 mg/Llimit 1 mg/L · 372.0× the limit
- CopperMetals · Reported level130 ug/Llimit 1 ug/L · 130.0× the limit
- BariumMetals · Reported level80 ug/Llimit 1 ug/L · 80.0× the limit
- TTHMDisinfection byproducts · Reported level50 ug/Llimit 1 ug/L · 50.0× the limit
- HAA5Disinfection byproducts · Reported level13 ug/Llimit 2 ug/L · 6.5× the limit
- VanadiumMetals · Reported level3.8 ug/Llimit 3 ug/L · 1.3× the limit
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
2.2× the national p90 (13.649999999999999 ng/L across detecting U.S. systems)
PFOS (Perfluorooctane sulfonic acid)
● Over EPA limit (1.3×)Measured 5.2 ng/LEPA limit 4 ng/LSample year 2023Samples 1 detect / 35
below national p90 (19.900000000000006 ng/L across detecting U.S. systems)
PFHxS (Perfluorohexane sulfonic acid)
● Below limitMeasured 4.2 ng/LEPA limit 10 ng/LSample year 2023Samples 1 detect / 35
below national p90 (12.049999999999997 ng/L across detecting U.S. systems)
PFPeA
● Detected (no federal limit)Measured 6.7 ng/LSample year 2023Samples 2 detect / 35
below national p90 (15.95999999999999 ng/L across detecting U.S. systems)
PFHxA
● Detected (no federal limit)Measured 7.1 ng/LSample year 2023Samples 1 detect / 35
near national p90 (12.190000000000003 ng/L across detecting U.S. systems)
PFBA
● Detected (no federal limit)Measured 6.4 ng/LSample year 2023Samples 2 detect / 35
below national p90 (18 ng/L across detecting U.S. systems)
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.
Historical readings · EPA Six-Year Review (2012–2019)
3 contaminants historically over EPA limits in Ontario, CA
Every U.S. public water system reports compliance-monitoring data to EPA. The Six-Year Review releases the 2012–2019 window as a single dataset — here's what your system reported, year by year. Values shown are the highest detection per analyte per year, compared to the federal MCL.
| Contaminant | Worst detection | EPA limit | Years (2012–2019) |
|---|---|---|---|
NITRITE worst: 2013 | 4.9 mg/L 4.9× | 1 mg/L | '12'13 |
NITRATE worst: 2017 | 14 mg/L 1.4× | 10 mg/L | '12'13'14'15'16'17'18'19 |
NITRATE NITRITE worst: 2017 | 12 mg/L 1.2× | 10 mg/L | '17 |
TTHM worst: 2019 | 0.077 mg/L 96% | 0.08 mg/L | '12'13'14'15'16'17'18'19 |
DBCP worst: 2012 | 0.00016 mg/L 80% below national p90 | 0.0002 mg/L | '12'13'14'15'16'17'18'19 |
HAA5 worst: 2015 | 0.043 mg/L within | 0.06 mg/L | '12'13'14'15'16'17'18'19 |
EDB worst: 2018 | 0.000021 mg/L within | 0.00005 mg/L | '18 |
ARSENIC worst: 2013 | 0.0024 mg/L within below national p90 | 0.01 mg/L | '13'17 |
FLUORIDE worst: 2012 | 0.5 mg/L within | 4 mg/L | '12'13'14'15'17 |
CHROMIUM worst: 2013 | 0.0088 mg/L within near national p90 | 0.1 mg/L | '12'13'14'15'17 |
BARIUM worst: 2013 | 0.14 mg/L within near national p90 | 2 mg/L | '13'14'15'17'19 |
DBAA worst: 2012 | 0.0059 mg/L | — | '12'13'14'15'16'17'18'19 |
DCAA worst: 2012 | 0.0041 mg/L | — | '12'13'14'15'16'17'18'19 |
MBAA worst: 2012 | 0.0018 mg/L | — | '12'13'14'15'16'18'19 |
MCAA worst: 2012 | 0.004 mg/L | — | '12'14'15'17'19 |
TCAA worst: 2012 | 0.0031 mg/L | — | '12'13'14'15'16'17'18'19 |
BROMODICHLOROMETHANE worst: 2012 | 0.023 mg/L | — | '12'13'14'15'16'17'18'19 |
BROMOFORM worst: 2012 | 0.013 mg/L | — | '12'13'14'15'16'17'18'19 |
CHLOROFORM worst: 2012 | 0.014 mg/L | — | '12'13'14'15'16'17'18'19 |
DIBROMOCHLOROMETHANE worst: 2012 | 0.025 mg/L | — | '12'13'14'15'16'17'18'19 |
PWSID CA3610034 · Source: EPA Six-Year Review 4 (2012–2019). Values are the highest detection in each calendar year; non-detect years are omitted. Year tags above show every year with a detection.
Physical & aggregate
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Specific ConductanceA measure of how well water conducts electricity, which tracks dissolved mineral content. | 508Reported levelPurchased Groundwater JCSD (870 Zone) | 1MCL | At or above the limit |
+By source (5)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +2 more
| |||
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 372 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | 1 mg/LMCL | At or above the limit |
+By source (5)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +2 more
| |||
| OdorA measure of detectable smell in the water. | 0.5Reported levelImported Water (WFA w/ SAWCO) | 3MCL | Within the limit |
| TurbidityA measure of cloudiness from suspended particles in the water. | 0.73 NTUReported levelOMUC's Entire Distribution System | 5 NTUMCL | Within the limit |
+By source (3)— OMUC's Entire Distribution System, Imported Water (WFA w/ SAWCO), 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 (5)— Local Groundwater, Purchased Groundwater JCSD (870 Zone), Imported Water (WFA w/ SAWCO) +2 more
| |||
| Bicarbonate | 156 mg/LReported levelLocal Groundwater | None set | Detected — no federal limit |
+By source (2)— Local Groundwater, Imported Water (WFA w/ SAWCO)
| |||
| HardnessA measure of dissolved calcium and magnesium minerals. | 200 mg/LReported levelPurchased Groundwater JCSD (870 Zone) | None set | Detected — no federal limit |
+By source (5)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +2 more
| |||
| pHA measure of how acidic or basic the water is. | 7.9Reported levelLocal Groundwater | None set | Detected — no federal limit |
+By source (3)— OMUC's Entire Distribution System, Local Groundwater, Imported Water (WFA w/ SAWCO)
| |||
| TOCTotal organic carbon — a measure of organic material dissolved in the water. | 2.3 mg/LReported levelImported Water (WFA w/ SAWCO) | None set | Detected — no federal limit |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| CopperA metal that enters water from corroding household plumbing. | 130 ug/LReported levelOMUC's Entire Distribution System | 1 ug/LAction level | At or above the limit |
| Vanadium | 3.8 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | 3 ug/LMCL | At or above the limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Imported Water (WFA w/ SAWCO), Purchased Groundwater CDA 2 (1110 Zone)
| |||
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 2.2 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | 10 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)
| |||
| AluminumA common element sometimes used as a treatment coagulant. | 41 ug/LReported levelImported Water (WFA w/ SAWCO) | 200 ug/LMCL | Within the limit |
+By source (2)— Purchased Groundwater CDA 2 (1110 Zone), Imported Water (WFA w/ SAWCO)
| |||
| SeleniumA trace element from natural deposits and industrial discharge. | 4.2 ug/LReported levelPurchased Groundwater JCSD (870 Zone) | 50 ug/LMCL | Within the limit |
+By source (3)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater CDA 2 (1110 Zone)
| |||
| LeadA toxic metal that leaches into water from old service lines, solder, and plumbing fixtures. | 0 ug/LReported levelOMUC's Entire Distribution System | 15 ug/LAction level | None detected |
| 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 (5)— Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone), Purchased Groundwater CDA 1 (870 Zone) +2 more
| |||
| MagnesiumA naturally occurring mineral that contributes to water hardness. | 9.4 mg/LReported levelImported Water (WFA w/ SAWCO) | None set | Detected — no federal limit |
+By source (5)— Imported Water (WFA w/ SAWCO), Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone) +2 more
| |||
| PotassiumA naturally occurring mineral from rock and soil. | 2.4 mg/LReported levelImported Water (WFA w/ SAWCO) | None set | Detected — no federal limit |
+By source (5)— Imported Water (WFA w/ SAWCO), Purchased Groundwater JCSD (870 Zone), Local Groundwater +2 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 (5)— Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone), Imported Water (WFA w/ SAWCO) +2 more
| |||
Disinfection byproducts
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| PerchlorateA chemical used in rocket fuel and fireworks that can also form during disinfection. | 1.5 ug/LReported levelLocal Groundwater | 6 ug/LMCL | Within the limit |
+By source (4)— Local Groundwater, Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +1 more
| |||
Disinfectants
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ChlorineA disinfectant added to drinking water to kill bacteria and viruses. | 0.98 mg/LReported levelOMUC's Entire Distribution System | 4 mg/LMRDL | Within the limit |
Inorganic chemicals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ChlorideA naturally occurring salt compound. | 98 mg/LReported levelPurchased Groundwater CDA 1 (870 Zone) | 500 mg/LMCL | Within the limit |
+By source (5)— Purchased Groundwater CDA 1 (870 Zone), Purchased Groundwater JCSD (870 Zone), Purchased Groundwater CDA 2 (1110 Zone) +2 more
| |||
| SulfateA naturally occurring mineral from rock and soil. | 34 mg/LReported levelImported Water (WFA w/ SAWCO) | 500 mg/LMCL | Within the limit |
+By source (5)— Imported Water (WFA w/ SAWCO), Purchased Groundwater JCSD (870 Zone), Local Groundwater +2 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 |
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 (4)— Purchased Groundwater JCSD (870 Zone), Local Groundwater, Imported Water (WFA w/ SAWCO) +1 more
| |||
| UraniumA naturally occurring radioactive metal from erosion of natural deposits. | 0.63 pCi/LReported levelPurchased Groundwater JCSD (870 Zone) | 20 pCi/LMCL | Within the limit |
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?
The 2024 Consumer Confidence Report for the Ontario, CA water utility lists 7 contaminants at or above the federal limit: Specific Conductance, Total Dissolved Solids, Copper, Barium, TTHM, HAA5, and Vanadium. Whether that means the water is "unsafe" depends on which contaminant, how long the exposure, and individual health factors. The table on this page shows the measured value, the federal threshold, and the regulated statistic used for compliance.
+What contaminants are in Ontario, CA tap water?
40 contaminants were measured in Ontario, CA's 2024 Consumer Confidence Report, spanning metals, physical & aggregate, and pfas ("forever chemicals"). 24 have an enforceable federal limit; the rest are detected but unregulated. Every measured value, in the utility's own units, is on this page.
+Which contaminants exceed federal limits in Ontario, CA tap water?
7 contaminants in Ontario, CA's 2024 report sit at or above the federal limit: Specific Conductance (508.0× the limit); Total Dissolved Solids (372.0× the limit); Copper (130.0× the limit); Barium (80.0× the limit); TTHM (50.0× the limit); HAA5 (6.5× the limit); Vanadium (1.3× the limit). The EPA enforces these limits against the regulated reporting statistic — typically a running annual average or 90th percentile — not a one-off sample spike.
+What is the worst contaminant in Ontario, CA tap water?
The contaminant with the highest measured value relative to its federal limit in the 2024 report is Specific Conductance, at 508.0× the federal threshold. It belongs to the physical & aggregate family of contaminants.
+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
Rancho CucamongaPomonaFontanaRialtoRiversideWest CovinaFullertonSanta AnaEl MonteIrvineMoreno ValleyCosta MesaHesperiaPasadenaCity of PerrisEast Valley Service AreaMills Service AreaHuntington BeachVictorvilleLos Angeles LADWPCity of MenifeeGlendaleCity of MurrietaSkinner Service AreaAll water systems →