Ofallon Pws, MO
Lead detected, under the action levels
Latest 90th-percentile lead: 1.48 ppb (monitoring period 2023-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Lead was measured in sampled homes but the 90th percentile is under both action levels. EPA's health goal for lead is zero, so test your own tap if your home was built before 1986 or anyone in it is pregnant or a young child.
Who runs the water here
Ofallon Pws serves about 32,515 people through 13,527 service connections, which makes it a large system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws surface water, in St. Charles County, Missouri. EPA system ID: MO6010588; phone on file: 636-379-3801. Ask them for your address in their service line inventory - every system had to publish one by Oct 2024.
Every lead result on file
That is down 1.69 ppb from 3.17 ppb in the period ending 2022. The highest 90th-percentile result EPA holds for Ofallon Pws is 3.17 ppb across 7 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 1.48 ppb |
| 2022 | 3.17 ppb |
| 2022 | 3.17 ppb |
| 2019 | 2.78 ppb |
| 2019 | 2.78 ppb |
| 2016 | 2.62 ppb |
| 2016 | 2.62 ppb |
Where this result ranks
Of the 1,674 Missouri systems with a lead result, the median latest reading is 1.04 ppb; 2 are over 15 ppb right now and 74 have gone over at some point. Ofallon Pws's 1.48 ppb sits at the 60th percentile in Missouri and the 63rd nationally (higher means more lead).
Other water systems in St. Charles County
17 other systems share St. Charles County; 5 of them have a higher latest lead result than Ofallon Pws. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| St Charles County Pwsd 2 | 100,587 | 2.28 ppb |
| St Charles Pws | 78,961 | 0 (not detected) |
| St Peters Pws | 52,575 | 0 (not detected) |
| Wentzville Pws | 41,784 | 4.77 ppb |
| St Paul Pws | 1,700 | 0 (not detected) |
| St Charles Co Pwsd 2 Augusta | 881 | 1.47 ppb |
| St Charles Pwsd 2 Foristell | 550 | 2.32 ppb |
| Mo American Jaxson | 535 | 0 (not detected) |
| Ecm Water & Sewer Authority - Flint Hill | 469 | 0 (not detected) |
| Portage Des Sioux Pws | 345 | 2.6 ppb |
Next steps for O Fallon, MO
Test your own tap with a certified lab first-draw sample; O Fallon, MO may offer free or low-cost kits through the utility. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Ofallon Pws whether it covers that cost before hiring anyone - many utilities now do.
These figures describe homes the utility sampled, not your tap. Only your service line record or a test of your own water answers the question for your house. Why sampled homes are the worst-case ones is in the guide to reading the number. Size matters more than most people expect: small vs large water systems.