Water quality for ZIP code 94561
ZIP 94561 covers Oakley, Knightsen, and Antioch in Contra Costa County, California, one of 43 ZIP codes in the county. 84 active public water systems serve the county; 21 had an EPA violation in the past three years.
Most likely your provider
Your location is within the outer bounds of this system's EPA service area.
Other community water systems in Contra Costa County
38 systems, nearest first| System | Serves | Status | Rules violated, 3 yr | Distance |
|---|---|---|---|---|
| Big Oak Mobile Home Park Water |
156 | 0 | 0.5 mi | |
| Knightsen Community Water System |
73 | 0 | 1.9 mi | |
| Dutch Slough Water Works |
49 | 1 | 2.5 mi | |
| Ccwd/brentwood Wtp |
0 | 0 | 2.5 mi | |
| Randall-Bold Water Treatment Plant |
1 | 0 | 2.6 mi | |
| Angler S Ranch #3 |
60 | 1 | 2.7 mi | |
| Anglers Subdivision 4 |
99 | 1 | 2.8 mi | |
| Bethel Island Mutual Water CO |
123 | 1 | 3.2 mi | |
| Farrar Park Property Owners |
140 | 0 | 3.2 mi | |
| Marina Mobile Manor |
75 | 0 | 3.2 mi | |
| Sandmound Mutual |
100 | 2 | 3.4 mi | |
| Willow Park Marina |
380 | 1 | 3.4 mi | |
| Delta Mutual Water Company |
333 | 1 | 3.5 mi | |
| Sandy Point Mobile Home Park |
67 | 2 | 3.5 mi | |
| Oakley Mutual Water Company |
170 | 2 | 3.6 mi | |
| Brentwood Brentwood |
64,513 | 0 | 4.3 mi | |
| Willow Mobile Home Park |
481 | 0 | 4.5 mi | |
| Bethel Island Estates |
200 | 0 | 4.6 mi | |
| Pleasantimes Mutual Water CO |
644 | 0 | 4.6 mi | |
| Riverview Water Association |
230 | 1 | 4.6 mi | |
| Russos Mobile Park |
110 | 2 | 4.7 mi | |
| Bethel Island MHC |
185 | 0 | 4.8 mi | |
| Orwood Resort |
350 | 2 | 5.7 mi | |
| City of Antioch Antioch |
116,781 | 0 | 5.8 mi | |
| Colonia Santa Maria |
32 | 2 | 6.3 mi |
Non-community systems in Contra Costa County (45: schools, campgrounds, workplaces, restaurants)
These systems serve places you visit rather than homes.
About this data
Water systems are matched to Contra Costa County, the county this ZIP code lies in, nearest to the ZIP code's centre first. Your exact provider depends on your address and connection; the largest community water system in a county is usually the city or town utility. Distances are measured to the centre of the service area EPA publishes for the system.
ZIP code areas and town boundaries come from the U.S. Census Bureau's 2020 ZCTA files.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The California records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.