Oak Park, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 4.52 ppb (monitoring period 2026-2026). 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.
About Oak Park
Oak Park serves about 54,583 people through 12,683 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 Cook County, Illinois. EPA system ID: IL0312250; phone on file: 708-358-5704. Ask them for your address in their service line inventory - every system had to publish one by Oct 2024.
Lead results over time
That is up 4.52 ppb from 0 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Oak Park is 5.08 ppb across 7 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 4.52 ppb |
| 2025 | 0 (not detected) |
| 2025 | 5.08 ppb |
| 2025 | 4.68 ppb |
| 2024 | 3.83 ppb |
| 2021 | 3.14 ppb |
| 2018 | 3.64 ppb |
How Oak Park compares
Of the 1,744 Illinois systems with a lead result, the median latest reading is 0 ppb; 22 are over 15 ppb right now and 152 have gone over at some point. Oak Park's 4.52 ppb sits at the 86th percentile in Illinois and the 89th nationally (higher means more lead).
Other water systems in Cook County
154 other systems share Cook County; 55 of them have a higher latest lead result than Oak Park. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Chicago | 2,721,308 | 6.4 ppb |
| Cicero | 83,000 | 5 ppb |
| Schaumburg | 75,750 | 0.87 ppb |
| Evanston | 74,486 | 6.5 ppb |
| Arlington Heights | 73,320 | 7.6 ppb |
| Palatine | 70,875 | 8.9 ppb |
| Skokie | 66,422 | 9.77 ppb |
| Des Plaines | 60,675 | 5.7 ppb |
| Oak Lawn | 58,362 | 9.3 ppb |
| Orland Park | 58,020 | 0 (not detected) |
What to do in your house
Test your own tap with a certified lab first-draw sample; Oak Park, IL 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 Oak Park 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. The lead result guide covers how utilities pick the homes they sample. Systems that went over once often dip back under; here is what that means.