Walnut, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 5.4 ppb (monitoring period 2025-2025). 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
Walnut serves about 1,311 people through 602 service connections, which makes it a small system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws groundwater, in Bureau County, Illinois. EPA system ID: IL0111100; phone on file: 815-379-2351. 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 up 2.45 ppb from 2.95 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Walnut is 5.4 ppb across 14 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 5.4 ppb |
| 2025 | 2.95 ppb |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2024 | 0 (not detected) |
| 2023 | 0 (not detected) |
| 2022 | 5 ppb |
| 2021 | 1.28 ppb |
| 2020 | 1.34 ppb |
| 2020 | 4.78 ppb |
| 2019 | 1.36 ppb |
| 2019 | 1.33 ppb |
| 2018 | 1.13 ppb |
| 2018 | 3.22 ppb |
Against other Illinois systems
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. Walnut's 5.4 ppb sits at the 89th percentile in Illinois and the 92nd nationally (higher means more lead).
Other water systems in Bureau County
23 other systems share Bureau County; 4 of them have a higher latest lead result than Walnut. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Princeton | 7,832 | 21 ppb |
| Spring Valley | 5,582 | 0 (not detected) |
| De Pue | 1,838 | 0 (not detected) |
| Ladd | 1,263 | 0 (not detected) |
| Wyanet | 886 | 19.5 ppb |
| Sheffield | 821 | 1.4 ppb |
| Tiskilwa | 740 | 0 (not detected) |
| Dalzell | 663 | 0 (not detected) |
| Lamoille | 660 | 22.3 ppb |
| Cherry | 490 | 13.8 ppb |
What to do in your house
Test your own tap with a certified lab first-draw sample; Walnut, 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 Walnut whether it covers that cost before hiring anyone - many utilities now do. Its latest copper 90th percentile is 1460 ppb (copper action level 1,300 ppb).
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. What a 90th-percentile result does and does not tell you: how to read a lead result. Systems that went over once often dip back under; here is what that means.