Plymouth 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.
Who runs the water here
Plymouth Water Supply serves about 378 people through 175 service connections, which makes it a very small system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws groundwater, in Cerro Gordo County, Iowa. EPA system ID: IA1759048; phone on file: 641-696-3363. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is up 2 ppb from 0 ppb in the period ending 2022. The highest 90th-percentile result EPA holds for Plymouth Water Supply is 5 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2 ppb |
| 2022 | 0 (not detected) |
| 2018 | 5 ppb |
How Plymouth Water Supply compares
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. Plymouth Water Supply's 2 ppb sits at the 63rd percentile in Iowa and the 71st nationally (higher means more lead).
Nearby utilities
8 other systems share Cerro Gordo County; 4 of them have a higher latest lead result than Plymouth Water Supply. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Mason City Water Department | 27,338 | 2.9 ppb |
| Clear Lake Water Department | 7,687 | 3.63 ppb |
| Rockwell Water Supply | 1,071 | 2.28 ppb |
| Ventura Water Works | 717 | 0 (not detected) |
| Thornton Water Supply | 400 | 2 ppb |
| Meservey Water Supply | 222 | 2 ppb |
| Swaledale Water Supply | 144 | 5.34 ppb |
| Long Beach Mobile Park | 50 | 0 (not detected) |
Next steps for Plymouth, IA
Test your own tap with a certified lab first-draw sample; Plymouth, 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 Plymouth 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. Size matters more than most people expect: small vs large water systems.