Rock Falls, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 3.1 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.
Rock Falls at a glance
Rock Falls serves about 8,620 people through 4,150 service connections, which makes it a medium-sized system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws groundwater, in Whiteside County, Illinois. EPA system ID: IL1950450; phone on file: 815-564-1366. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is down 1.26 ppb from 4.36 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Rock Falls is 7.6 ppb across 8 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2028 | 3.1 ppb |
| 2025 | 4.36 ppb |
| 2025 | 0 (not detected) |
| 2025 | 3.1 ppb |
| 2025 | 2.4 ppb |
| 2023 | 2.1 ppb |
| 2020 | 2.5 ppb |
| 2017 | 7.6 ppb |
How Rock Falls 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. Rock Falls's 3.1 ppb sits at the 81st percentile in Illinois and the 83rd nationally (higher means more lead).
Other water systems in Whiteside County
10 other systems share Whiteside County; 1 of them has a higher latest lead result than Rock Falls. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Il American-Sterling | 14,782 | 0 (not detected) |
| Morrison | 4,188 | 4.6 ppb |
| Fulton | 3,346 | 0 (not detected) |
| Prophetstown | 1,946 | 0 (not detected) |
| Erie | 1,479 | 1.2 ppb |
| Albany | 846 | 1.6 ppb |
| Tampico | 689 | 0 (not detected) |
| Lyndon | 537 | 0 (not detected) |
| Country Acres Mhp (Whiteside County) | 232 | 0 (not detected) |
| Honeycutt Hill Mhp Llc | 75 | 0 (not detected) |
What to do in your house
Test your own tap with a certified lab first-draw sample; Rock Falls, 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 Rock Falls 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. The action level is dropping - the 10 ppb rule from 2027.