Is Ontario, OR Tap Water Safe? Quality & Contaminants

What was found in Ontario's water

The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.

Contaminant	Level vs EPA limit	Suppliers	Source
Nitrate	2020 µg/L 20% of the EPA limit 10000 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Nitrate-Nitrite	1147 µg/L 11% of the EPA limit 10000 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Fluoride	705.3 µg/L 18% of the EPA limit 4000 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Copper	306.25 µg/L 24% of the EPA limit 1300 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2018	1/1	SYR4
TTHM	78.085 µg/L 98% of the EPA limit 80 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Barium	60.63 µg/L 3% of the EPA limit 2000 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Total Haloacetic Acids (HAA5)	42.025 µg/L 70% of the EPA limit 60 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Lithium	38.4 µg/L No EPA limit set Main supplier: ONTARIO, CITY OF · 14,465 people · 2025	1/1	UCMR-5
Lead	6.705 µg/L 45% of the EPA limit 15 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2018	1/1	SYR4
Arsenic	5.046 µg/L 50% of the EPA limit 10 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Gross Alpha, Excl. Radon And U	3.13 pCi/L 21% of the EPA limit 15 pCi/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Combined Uranium	2.8625 µg/L 9.5% of the EPA limit 30 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Chromium	1.285 µg/L 1.3% of the EPA limit 100 µg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2019	1/1	SYR4
Lead	0.0021 mg/L 14% of the EPA limit 0.0150 mg/L Main supplier: ONTARIO, CITY OF · 14,465 people · 2024	1/1	LCR

Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the 95th percentile of the system's samples — over 100% is worth reading, but is not by itself a violation. Formal violations are listed separately. These are the utilities' own EPA-reported results, not a city-wide average. A detection means the lab measured the substance — it isn't the same as exceeding a legal limit. Hover a source tag to see the EPA program and years behind each figure.

Water suppliers serving Ontario

Supplier	Population served
ONTARIO, CITY OF	14,465

Frequently asked questions about Ontario tap water

Is Ontario tap water safe to drink?

EPA testing detected 14 contaminants in the water serving Ontario. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.

How many water suppliers serve Ontario?

1 public water supplier report drinking-water monitoring for Ontario, Oregon to the EPA. Each is listed above with its population served.

What contaminants are in Ontario's water?

The contaminants EPA monitoring detected in Ontario include Nitrate, Nitrate-Nitrite, Fluoride, Copper, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.

Where does this data come from?

Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.