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Tap water quality report

O Fallon, IL

EPA monitoring detected 15 contaminants across the 2 water suppliers serving O Fallon. A detection doesn't automatically mean the water is unsafe — see the level at the main supplier for each below, with its EPA source and period.

2
water suppliers
47,183
people served
15
contaminants found
Illinois rankings Lead in Illinois PFAS in Illinois

What was found in O Fallon'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.

ContaminantLevel vs EPA limitSuppliersSource
Copper
584.5 µg/L 45%
of the EPA limit 1300 µg/L
Main supplier: O FALLON · 46,603 people · 2017
1/2 SYR4
TTHM
87.4 µg/L 109%
of the EPA limit, at the 95th percentile of samples — 80 µg/L
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Chloroform
73.35999999999999 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Total Haloacetic Acids (HAA5)
72.93999999999997 µg/L 122%
of the EPA limit, at the 95th percentile of samples — 60 µg/L
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Trichloroacetic Acid
36.66 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Dichloroacetic Acid
34.63999999999999 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Bromodichloromethane
14.179999999999998 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Lithium
11.6 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2024
1/2 UCMR-5
Monochloroacetic Acid
7.96 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Monobromoacetic Acid
3.934999999999999 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Dibromochloromethane
3.1 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Dibromoacetic Acid
2.4250000000000003 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2019
1/2 SYR4
Lead
2 µg/L 13%
of the EPA limit 15 µg/L
Main supplier: O FALLON · 46,603 people · 2017
1/2 SYR4
Pfba
0.0130 µg/L
No EPA limit set
Main supplier: O FALLON · 46,603 people · 2024
1/2 UCMR-5
Lead
0.0022 mg/L 15%
of the EPA limit 0.0150 mg/L
Main supplier: O FALLON · 46,603 people · 2025
2/2 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 O Fallon

SupplierPopulation served
O FALLON 46,603
VALLEY VIEW ESTATES 580

Frequently asked questions about O Fallon tap water

Is O Fallon tap water safe to drink?

EPA testing detected 15 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?

2 public water suppliers report drinking-water monitoring for O Fallon, Illinois 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 Copper, TTHM, Chloroform, Total Haloacetic Acids (HAA5), Trichloroacetic Acid. 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.