Is O'Fallon, IL tap water safe?
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data for O'Fallon Water System. 1 PFAS were detected below the limits.
O'Fallon Water System supplies O'Fallon (46,603 people).
Water system
O'Fallon Water System
46,603 people · Purchased surface water · EPA ID IL1631100
Buys treated water from Illinois American Water – East St Louis.
| PFAS | Highest average | Limit |
|---|---|---|
| PFOA Not detected | – | 4 ppt |
| PFOS Not detected | – | 4 ppt |
| PFHxS Not detected | – | 10 ppt |
| PFNA Not detected | – | 10 ppt |
| HFPO-DA (GenX) Not detected | – | 10 ppt |
ppt = parts per trillion. "Highest average" is the highest average at any of the system's entry points, the way EPA compares results with the limits.
Lead: 0 ppb at the 90th percentile (Nov 2026, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0
Across Illinois, 13 of 479 water systems EPA tested had PFAS above a 2024 federal limit, and 18 systems were above the lead action level in results from the last five years. Illinois results.
O'Fallon homes and lead pipes
Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. How to check your own line.
Housing: Census American Community Survey 2020–2024 5-year estimates for O'Fallon city (tables B25034, B25003). Estimates for small places have a margin of error.
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| Belleville 7 mi Illinois American Water – Homer Township | None above limits | 0 ppb |
| Edwardsville 14 mi Edwardsville Water System | None above limits | 0 ppb |
| Granite City 15 mi Illinois American Water – Granite City | None above limits | 6 ppb |
| Alton 25 mi Illinois American Water – Alton | None above limits | 3 ppb |
| Springfield 84 mi Springfield Water System | None above limits | 0 ppb |
| Decatur 102 mi Decatur Water System | None above limits | 0 ppb |
O'Fallon ZIP codes (1)
- 62269
Questions
Is O'Fallon tap water safe to drink?
O'Fallon Water System has had no health-based violations since 2016. Utility data can't show lead from your own pipes: if your home was built before 1986, test your tap. Your utility's annual Consumer Confidence Report is the official summary.
Who supplies water in O'Fallon, IL?
O'Fallon Water System, which serves 46,603 people.
Does O'Fallon tap water have PFAS?
O'Fallon Water System had 1 PFAS detected at least once in EPA's 2023–2025 testing, all with averages below the federal limits.
Do O'Fallon homes have lead pipes?
Census estimates put 26% of O'Fallon homes as built before 1980 (Illinois: 64%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. O'Fallon Water System's service line inventory says what your line is made of. The only way to know for your home is to check the line where it enters the house and test your tap.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.