Marengo, IL
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (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. The latest 90th-percentile result was reported as 0 (not detected at the lab's limit). That says the sampled homes were low, not that your home has no lead service line. Check your utility's service line inventory for your address.
Marengo at a glance
Marengo serves about 7,572 people through 2,810 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 Mchenry County, Illinois. EPA system ID: IL1110650; phone on file: 815-568-7112. They can tell you what your service line is made of and whether they pay to replace it.
Lead results over time
Against the period ending 2025 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Marengo is 3.4 ppb across 8 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2028 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2024 | 3.4 ppb |
| 2021 | 1.9 ppb |
| 2018 | 0 (not detected) |
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. Marengo's reported as 0 (not detected) sits at the 50th percentile in Illinois and the 36th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Other water systems in Mchenry County
31 other systems share Mchenry County; 20 of them have a higher latest lead result than Marengo. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Crystal Lake | 40,661 | 6.8 ppb |
| Algonquin | 30,700 | 1.96 ppb |
| Lake In The Hills | 28,661 | 0 (not detected) |
| Huntley | 28,495 | 1.1 ppb |
| Woodstock | 25,630 | 1.5 ppb |
| Mchenry | 22,335 | 6.7 ppb |
| Cary | 17,826 | 1.7 ppb |
| Harvard | 9,469 | 7.1 ppb |
| Il American-Whispering Hills | 8,300 | 0 (not detected) |
| Fox River Grove | 4,702 | 6.4 ppb |
What to do in your house
Look up your address in Marengo's service line inventory. If it says lead, galvanized or unknown, test your tap. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Marengo 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. Why sampled homes are the worst-case ones is in the guide to reading the number. A zero today does not rule out a jump later - the rules are tightening in 2027.