Lanark, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 5.1 ppb (monitoring period 2026-2028). 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
Lanark serves about 1,504 people through 691 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 Carroll County, Illinois. EPA system ID: IL0150100; phone on file: 815-493-6832. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is up 5.1 ppb from 0 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Lanark is 12.2 ppb across 8 monitoring periods, none of them over 15 ppb (1 over 10 ppb).
| Period ending | 90th-percentile lead |
|---|---|
| 2028 | 5.1 ppb |
| 2025 | 0 (not detected) |
| 2025 | 12.2 ppb over 10 |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2024 | 0 (not detected) |
| 2021 | 0 (not detected) |
| 2018 | 0 (not detected) |
How Lanark 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. Lanark's 5.1 ppb sits at the 88th percentile in Illinois and the 91st nationally (higher means more lead).
Other water systems in Carroll County
9 other systems share Carroll County; 2 of them have a higher latest lead result than Lanark. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Savanna | 3,020 | 0 (not detected) |
| Thomson Maximum Security Center | 2,166 | - |
| Mount Carroll | 1,479 | 1.1 ppb |
| Milledgeville | 989 | 5.45 ppb |
| Shannon | 801 | 0 (not detected) |
| Thomson | 600 | 0.59 ppb |
| Chadwick | 523 | 5.33 ppb |
| Mountain Vale Village Mhp | 388 | - |
| Carroll Heights Utilities Company | 80 | 3 ppb |
Your move
Test your own tap with a certified lab first-draw sample; Lanark, 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 Lanark 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. What a 90th-percentile result does and does not tell you: how to read a lead result. Size matters more than most people expect: small vs large water systems.