Diamond A Mutual Water Company, CA
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2024-2026). 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.
Who runs the water here
Diamond A Mutual Water Company serves about 640 people through 195 service connections, which makes it a small system under EPA's size classes. It is privately owned and draws groundwater, in Sonoma County, California. EPA system ID: CA4900562; phone on file: 707-337-6047. 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 2023 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Diamond A Mutual Water Company is 0 ppb across 5 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 0 (not detected) |
| 2023 | 0 (not detected) |
| 2020 | 0 (not detected) |
| 2017 | 0 (not detected) |
| 2016 | 0 (not detected) |
Against other California systems
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. Diamond A Mutual Water Company's reported as 0 (not detected) sits at the 39th percentile in California and the 24th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Neighbouring systems
128 other systems share Sonoma County; 24 of them have a higher latest lead result than Diamond A Mutual Water Company. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Santa Rosa, City Of | 178,452 | 1.32 ppb |
| Petaluma, City Of | 61,427 | 0 (not detected) |
| Rohnert Park, City Of | 43,821 | 0 (not detected) |
| Windsor, Town Of | 25,561 | 0 (not detected) |
| Valley Of The Moon Water District | 23,140 | 0 (not detected) |
| Healdsburg, City Of | 10,972 | 0 (not detected) |
| Sonoma, City Of | 10,619 | 0 (not detected) |
| Cloverdale, City Of | 8,710 | 0 (not detected) |
| California-American Larkfield (Puc) | 7,911 | 6 ppb |
| Sebastopol, City Of | 7,522 | 0 (not detected) |
Your move
Look up your address in Diamond A Mutual Water Company'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 Diamond A Mutual Water Company 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. Small systems behave differently: why small systems go over more often.