Is O'Fallon, MO Tap Water Safe? Quality & Contaminants

What was found in O'Fallon's water

The highest level seen across the city's suppliers, the EPA limit for each, and where the figure comes from.

Contaminant	Level vs EPA limit	Suppliers	Source
Fluoride	1840 µg/L 46% of the EPA limit 4000 µg/L	5/5	SYR4
Nitrate-Nitrite	1610 µg/L 16% of the EPA limit 10000 µg/L	5/5	SYR4
Copper	577 µg/L 44% of the EPA limit 1300 µg/L	5/5	SYR4
Barium	147 µg/L 7.4% of the EPA limit 2000 µg/L	5/5	SYR4
TTHM	85.3 µg/L 107% of the EPA limit, in the worst sample — 80 µg/L	5/5	SYR4
Lithium	71.3 µg/L No EPA limit set	2/5	UCMR-5
Chloroform	50.1 µg/L No EPA limit set	5/5	SYR4
Total Haloacetic Acids (HAA5)	41.7 µg/L 70% of the EPA limit 60 µg/L	4/5	SYR4
Dichloroacetic Acid	36.3 µg/L No EPA limit set	5/5	SYR4
Dibromochloromethane	21.9 µg/L No EPA limit set	5/5	SYR4
Bromodichloromethane	20.3 µg/L No EPA limit set	5/5	SYR4
Lead	16.7 µg/L 111% of the EPA limit, in the worst sample — 15 µg/L	5/5	SYR4
Gross Alpha, Excl. Radon And U	15 pCi/L 100% of the EPA limit 15 pCi/L	1/5	SYR4
Monobromoacetic Acid	12.5 µg/L No EPA limit set	4/5	SYR4
Selenium	11 µg/L 22% of the EPA limit 50 µg/L	1/5	SYR4
Trichloroacetic Acid	10.1 µg/L No EPA limit set	5/5	SYR4
Monochloroacetic Acid	9.7 µg/L No EPA limit set	1/5	SYR4
Bromoform	9.33 µg/L No EPA limit set	3/5	SYR4
Chromium	7.48 µg/L 7.5% of the EPA limit 100 µg/L	4/5	SYR4
Combined Radium (-226 And -228)	5.8 pCi/L 116% of the EPA limit, in the worst sample — 5 pCi/L	4/5	SYR4
Dibromoacetic Acid	3.9 µg/L No EPA limit set	4/5	SYR4
Xylenes, Total	2.87 µg/L 0% of the EPA limit 10000 µg/L	2/5	SYR4
Arsenic	2.32 µg/L 23% of the EPA limit 10 µg/L	1/5	SYR4
Atrazine	0.3300 µg/L 11% of the EPA limit 3 µg/L	1/5	SYR4
Pfba	0.0065 µg/L No EPA limit set	2/5	UCMR-5
Pfpea	0.0034 µg/L No EPA limit set	1/5	UCMR-5
Lead	0.0015 mg/L 9.9% of the EPA limit 0.0150 mg/L	5/5	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 single worst sample on record — 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 O'Fallon

Supplier	Population served
ST CHARLES COUNTY PWSD 2	100,587
OFALLON PWS	32,515
ST PAUL PWS	1,700
ST CHARLES CO PWSD 2 AUGUSTA	881
ST CHARLES CO PWSD 2 - SUMAC RIDGE	103

Frequently asked questions about O'Fallon tap water

Is O'Fallon tap water safe to drink?

EPA testing detected 27 contaminants in the water serving O'Fallon. 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 O'Fallon?

5 public water suppliers report drinking-water monitoring for O'Fallon, Missouri to the EPA. Each is listed above with its population served.

What contaminants are in O'Fallon's water?

The contaminants EPA monitoring detected in O'Fallon include Fluoride, Nitrate-Nitrite, Copper, Barium, TTHM. The full list, with the highest level found 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.