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ZIP Code 94561 Water Quality
California · 44,728 people served · 8 water systems
F
FailingZIP code 94561 is in California and is a small city from a drinking-water-service perspective, with 44,728 people served by 8 EPA-registered public water systems. It corresponds to OAKLEY.
Within ZIP code 94561, the EPA Safe Drinking Water Information System (SDWIS) records 54 health-based violations during the past five years across 8 water systems serving this postal area. The grade of F reflects the aggregate compliance pattern, not the current daily water quality.
Last updated: 2026-05-18 · Source: EPA SDWIS
ZIP Code Location
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Cities in ZIP 94561
Water Systems Serving 94561
DUTCH SLOUGH WATER WORKS
PWSID: CA0707519
49 served
OAKLEY MUTUAL WATER COMPANY
PWSID: CA0706004
170 served
DELTA MUTUAL WATER COMPANY
PWSID: CA0707573
333 served
WILLOW PARK MARINA
PWSID: CA0707507
380 served
KNIGHTSEN COMMUNITY WATER SYSTEM
PWSID: CA0707547
73 served
DIABLO WATER DISTRICT
PWSID: CA0710007
43,357 served
BIG OAK MOBILE HOME PARK WATER
PWSID: CA0707588
156 served
CAMINO MOBILEHOME
PWSID: CA0707598
210 served
About ZIP-code water data
Postal-code level water quality data is built up from the underlying water systems — multiple ZIPs may share a single utility, and a single ZIP can span multiple utilities. For property-level information, contact the specific utility serving your address. EPA data on this page was last refreshed on 2026-05-18.
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