Waterloo, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 1.1 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.
Waterloo at a glance
Waterloo serves about 10,190 people through 4,942 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 groundwater, in Monroe County, Illinois. EPA system ID: IL1330300; phone on file: 618-939-8600. They can tell you what your service line is made of and whether they pay to replace it.
Every lead result on file
Against the period ending 2025 (1.4 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Waterloo is 4.4 ppb across 8 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2028 | 1.1 ppb |
| 2025 | 1.4 ppb |
| 2025 | 4.4 ppb |
| 2025 | 0 (not detected) |
| 2025 | 2.5 ppb |
| 2022 | 0 (not detected) |
| 2019 | 0 (not detected) |
| 2016 | 0 (not detected) |
Where this result ranks
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. Waterloo's 1.1 ppb sits at the 62nd percentile in Illinois and the 57th nationally (higher means more lead).
Nearby utilities
5 other systems share Monroe County; 3 of them have a higher latest lead result than Waterloo. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Columbia | 11,129 | 0 (not detected) |
| Fountain Water District | 4,350 | 5.7 ppb |
| Valmeyer | 1,233 | 0 (not detected) |
| Hecker | 429 | 1.9 ppb |
| Maeystown | 340 | 5 ppb |
Next steps for Waterloo, IL
Test your own tap with a certified lab first-draw sample; Waterloo, 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 Waterloo 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. Systems that went over once often dip back under; here is what that means.