Is O'Fallon, MO 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 Missouri American Water – St Louis St Charles Counties. 1 PFAS were detected below the limits.
3 public water systems serve parts of O'Fallon. The largest, Missouri American Water – St Louis St Charles Counties, serves 1.1 million people. Your water bill names your system.
Largest system
Missouri American Water – St Louis St Charles Counties
1.1 million people · Surface water · EPA ID MO6010716
Buys treated water from St Louis City Public Water System.
| 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 (Dec 2025, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0
Full Missouri American Water – St Louis St Charles Counties results
Across Missouri, 6 of 227 water systems EPA tested had PFAS above a 2024 federal limit, and 3 systems were above the lead action level in results from the last five years. Missouri 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.
Other water systems serving O'Fallon
- St Charles County Public Water Supply District 2100,587 people · Purchased surface water · Missouri · reported ZIPs hereLithium above screening level
- Ofallon Public Water System32,515 people · Purchased surface water · Missouri · reported ZIPs hereLithium above screening level
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| St. Peters 6 mi Missouri American Water – St Louis St Charles Counties | None above limits | 0 ppb |
| Wentzville 8 mi Wentzville Public Water System | None above limits | 4.77 ppb |
| St. Charles 11 mi Missouri American Water – St Louis St Charles Counties | None above limits | 0 ppb |
| Chesterfield 11 mi Missouri American Water – St Louis St Charles Counties | None above limits | 0 ppb |
| Maryland Heights 14 mi Missouri American Water – St Louis St Charles Counties | None above limits | 0 ppb |
| Wildwood 14 mi Missouri American Water – St Louis St Charles Counties | None above limits | 0 ppb |
O'Fallon ZIP codes (2)
- 63366
- 63368
Questions
Is O'Fallon tap water safe to drink?
Missouri American Water – St Louis St Charles Counties 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, MO?
3 public water systems serve parts of O'Fallon. The largest is Missouri American Water – St Louis St Charles Counties (1.1 million people). Your water bill names your system. The EPA ID is also on your utility's Consumer Confidence Report.
Does O'Fallon tap water have PFAS?
Missouri American Water – St Louis St Charles Counties 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 9% of O'Fallon homes as built before 1980 (Missouri: 53%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. Missouri American Water – St Louis St Charles Counties'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.