City Of Mountain House, CA
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2025-2025). 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.
About City Of Mountain House
City Of Mountain House serves about 26,400 people through 8,323 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 surface water, in San Joaquin County, California. EPA system ID: CA3910027; phone on file: 209-831-5648. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
Against the period ending 2024 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for City Of Mountain House is 5.4 ppb across 10 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 0 (not detected) |
| 2024 | 0 (not detected) |
| 2023 | 0 (not detected) |
| 2022 | 0 (not detected) |
| 2021 | 0 (not detected) |
| 2020 | 2.1 ppb |
| 2019 | 0.9 ppb |
| 2018 | 2 ppb |
| 2017 | 1.4 ppb |
| 2016 | 5.4 ppb |
How City Of Mountain House compares
Of the 2,884 California systems with a lead result, the median latest reading is 0 ppb; 30 are over 15 ppb right now and 215 have gone over at some point. City Of Mountain House's reported as 0 (not detected) sits at the 57th percentile in California and the 39th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Neighbouring systems
92 other systems share San Joaquin County; 12 of them have a higher latest lead result than City Of Mountain House. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| City Of Stockton | 192,702 | 0 (not detected) |
| California Water Service - Stockton | 182,775 | 0 (not detected) |
| Tracy, City Of | 98,215 | 0 (not detected) |
| Manteca, City Of | 84,928 | 0.4 ppb |
| Lodi, City Of | 67,093 | 0 (not detected) |
| City Of Lathrop | 38,596 | 0 (not detected) |
| Ripon, City Of | 15,753 | 0 (not detected) |
| Escalon, City Of | 7,232 | 0 (not detected) |
| San Joaquin County - Lincoln Village | 5,841 | 0 (not detected) |
| San Joaquin County-Mokelumne Acres | 3,802 | 0 (not detected) |
Next steps for Mountain House, CA
Look up your address in City Of Mountain House'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 City Of Mountain House 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. The lead result guide covers how utilities pick the homes they sample. A zero today does not rule out a jump later - the rules are tightening in 2027.