Rock Valley Water Supply, IA
Lead detected, under the action levels
Latest 90th-percentile lead: 2 ppb (monitoring period 2023-2025). 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.
About Rock Valley Water Supply
Rock Valley Water Supply serves about 4,059 people through 1,866 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 Sioux County, Iowa. EPA system ID: IA8482096; phone on file: 712-470-1936. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Every lead result on file
Against the period ending 2021 (3 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Rock Valley Water Supply is 4 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2 ppb |
| 2021 | 3 ppb |
| 2018 | 4 ppb |
Where this result ranks
Of the 1,066 Iowa systems with a lead result, the median latest reading is 1.4 ppb; 4 are over 15 ppb right now and 36 have gone over at some point. Rock Valley Water Supply's 2 ppb sits at the 67th percentile in Iowa and the 72nd nationally (higher means more lead).
Other water systems in Sioux County
14 other systems share Sioux County; 6 of them have a higher latest lead result than Rock Valley Water Supply. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Sioux Center Municipal Water Department | 8,231 | 4.4 ppb |
| Orange City Municipal Water Department | 6,267 | 0 (not detected) |
| Southern Sioux County Rural Water | 5,420 | 2.1 ppb |
| Rural Water System #1 | 3,428 | 1.2 ppb |
| Hawarden Water Supply | 2,700 | 0 (not detected) |
| Hull Water Supply | 2,384 | 1.8 ppb |
| Rock Valley Rural Water District | 2,250 | 2.4 ppb |
| Alton Municipal Water Department | 1,248 | 0.87 ppb |
| Hospers Municipal Water Dept | 718 | 6.1 ppb |
| Boyden Municipal Water Supply | 709 | 2.2 ppb |
Your move
Test your own tap with a certified lab first-draw sample; Rock Valley, IA 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 Valley Water Supply 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. Systems that went over once often dip back under; here is what that means.