Is O Fallon Tap Water Safe? Quality Report

Water source: SWP
Ownership: Local government
Counties served: St. Clair

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

health-based violations

violations on file

still open

Violation	Type	Status	Period
MCL	Health-based	Archived	1999-07-01 → 1999-07-31
MCL	Health-based	Archived	1999-07-01 → 1999-07-31
MCL	Health-based	Archived	1998-04-01 → 1998-04-30
MCL	Health-based	Archived	1998-04-01 → 1998-04-30
MCL	Health-based	Archived	1998-04-01 → 1998-04-30
MCL	Health-based	Archived	1998-04-01 → 1998-04-30
MCL	Health-based	Archived	1996-08-01 → 1996-08-31
MCL	Health-based	Archived	1996-08-01 → 1996-08-31
MCL	Health-based	Archived	1996-08-01 → 1996-08-31
MCL	Health-based	Archived	1996-03-01 → 1996-03-31

PFAS detected

PFAS are industrial “forever chemicals”. These are the EPA's latest nationwide test results (2023–2025).

Contaminant	Max	Detection rate	Period
Pfba	0.0130 µg/L	4/4	2024

Other contaminants detected

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 this system's samples — over 100% is worth reading, but is not by itself a violation. Where a single sample came in higher than that percentile, it is noted under the bar. Formal violations are listed separately.

Contaminant	Level vs EPA limit	Detection rate	Source	Period
Bromodichloromethane	14.18 µg/L No EPA limit set worst single sample: 17.9 µg/L	125/125	SYR4	2012–2019
Chloroform	73.36 µg/L No EPA limit set worst single sample: 104.1 µg/L	125/125	SYR4	2012–2019
Dichloroacetic Acid	34.64 µg/L No EPA limit set worst single sample: 46.6 µg/L	125/125	SYR4	2012–2019
TTHM	87.4 µg/L 109% of the EPA limit, at the 95th percentile of samples — 80 µg/L worst single sample: 120.4 µg/L	125/125	SYR4	2012–2019
Total Haloacetic Acids (HAA5)	72.94 µg/L 122% of the EPA limit, at the 95th percentile of samples — 60 µg/L worst single sample: 92.5 µg/L	125/125	SYR4	2012–2019
Trichloroacetic Acid	36.66 µg/L No EPA limit set worst single sample: 59.7 µg/L	125/125	SYR4	2012–2019
Dibromochloromethane	3.1 µg/L No EPA limit set worst single sample: 3.3 µg/L	57/125	SYR4	2012–2019
Monobromoacetic Acid	3.935 µg/L No EPA limit set worst single sample: 4.5 µg/L	54/125	SYR4	2012–2019
Copper	584.5 µg/L 45% of the EPA limit 1300 µg/L worst single sample: 758 µg/L	51/60	SYR4	2014–2017
Monochloroacetic Acid	7.96 µg/L No EPA limit set worst single sample: 8 µg/L	29/125	SYR4	2012–2019
Dibromoacetic Acid	2.425 µg/L No EPA limit set worst single sample: 2.9 µg/L	20/125	SYR4	2012–2019
Lead	0.0022 mg/L 15% of the EPA limit 0.0150 mg/L	19/19	LCR	2025
Lead	2 µg/L 13% of the EPA limit 15 µg/L	9/60	SYR4	2014–2017
Lithium	11.6 µg/L No EPA limit set	2/4	UCMR-5	2024

29 contaminants tested, none detected

11Cl-PF3OUdS4:2 Fts6:2 Fts8:2 Fts9Cl-PF3ONSAdonaBromoformHfpo-DaNetfosaaNfdhaNmefosaaPFBSPfdaPfdoaPfeesaPfhpaPfhpsPfhxaPFHXSPfmbaPfmpaPFNAPFOAPFOSPfpeaPfpesPftaPftrdaPfuna

Utility contact

Contact: BELL, HEIDE
Phone: 618-624-4500
Email: [email protected]

Frequently asked questions about O Fallon

Is O Fallon tap water safe to drink?

EPA monitoring detected 15 contaminants in O Fallon's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in O Fallon's water?

EPA monitoring detected Bromodichloromethane, Chloroform, Dichloroacetic Acid, TTHM, Total Haloacetic Acids (HAA5), and others. The full list with the level and data source for each is above.

How many people does O Fallon serve?

O Fallon reports serving 46,603 people in Illinois, per its EPA record.

Has O Fallon had any water quality violations?

The EPA has 70 violations on file for O Fallon, of which 44 are health-based (a contaminant limit or required treatment was breached) and 0 remain open. The rest are monitoring or reporting failures.

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.