Diablo Water District, CA
Lead detected, under the action levels
Latest 90th-percentile lead: 1.9 ppb (monitoring period 2020-2022). 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.
Diablo Water District at a glance
Diablo Water District serves about 47,158 people through 13,773 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 Contra Costa County, California. EPA system ID: CA0710007; phone on file: 925-625-3798. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Diablo Water District's lead record
That is up 1.9 ppb from 0 ppb in the period ending 2019. The highest 90th-percentile result EPA holds for Diablo Water District is 1.9 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2022 | 1.9 ppb |
| 2019 | 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. Diablo Water District's 1.9 ppb sits at the 78th percentile in California and the 69th nationally (higher means more lead).
Neighbouring systems
38 other systems share Contra Costa County; 5 of them have a higher latest lead result than Diablo Water District. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Contra Costa Water District | 210,500 | 0 (not detected) |
| City Of Antioch | 116,781 | 0 (not detected) |
| Brentwood | 64,513 | 0 (not detected) |
| City Of Pittsburg | 62,500 | 0 (not detected) |
| City Of Martinez | 31,015 | 0 (not detected) |
| Golden State Water Company - Bay Point | 23,765 | 0.49 ppb |
| Town Of Discovery Bay | 16,790 | 0 (not detected) |
| Pleasantimes Mutual Water Co | 644 | 0.5 ppb |
| Clayton Palms Water | 549 | - |
| Willow Mobile Home Park | 481 | 10 ppb |
Next steps for Oakley, CA
Test your own tap with a certified lab first-draw sample; Oakley, CA 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 Diablo Water District 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. What a 90th-percentile result does and does not tell you: how to read a lead result. Size matters more than most people expect: small vs large water systems.