California
San Luis Obispo County drinking water quality
172 active public water systems serve 292,764 people in San Luis Obispo County. 118 are compliant, 54 had at least one EPA violation in the past three years, 0 are designated serious violators, and 9 carry a health flag.
Needs attention
Community water systems
72 systems, largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Bassi Ranch Mutual Water Co. |
85 | 2 | 1 | |
|
Ken Mar Gardens |
84 | 2 | 0 | |
|
Baron Canyon Mutual Water Co. |
81 | 0 | 0 | |
|
Laguna Negra Mutual Water Co. |
80 | 1 | 0 | |
|
Avila Valley Mutual Water CO |
75 | 0 | 0 | |
|
H2o, INC |
70 | 1 | 0 | |
|
Lopez Project |
69 | 1 | 0 | |
|
Monte Sereno Mutual Benefit Water |
65 | 0 | 0 | |
|
Anza Vineyard Estates Mutual Water CO |
60 | 0 | 0 | |
|
Country Hills Estates |
60 | 0 | 0 | |
|
Rim Rock Water Company |
55 | 2 | 0 | |
|
Rancho Salinas Mbwc |
50 | 0 | 0 | |
|
Bear Valley Water Company |
45 | 2 | 1 | |
|
Rancho Nipomo Water Company |
44 | 0 | 0 | |
|
Almira Water Association |
40 | 2 | 0 | |
|
Terra de Oro Water Company |
38 | 0 | 0 | |
|
Higuera Apartments |
30 | 3 | 2 | |
|
Mustang Springs Mutual Water |
30 | 0 | 0 | |
|
Ada's Lodges |
25 | 1 | 0 | |
|
Chorro Valley Pipeline Slo County |
0 | 0 | 0 | |
|
Nacimiento Water Project |
0 | 0 | 0 | |
|
Slo Csa No. 10 Cayucos Wtp |
0 | 0 | 0 |
Non-community systems (100: schools, campgrounds, workplaces, restaurants)
These systems serve places people visit rather than homes.
Inactive systems (89, no longer operating or reporting)
Kept for the record and excluded from the county totals above. Browse inactive systems.
About this data
Totals cover active systems. Systems serving more than one county are counted in each county. EPA counts the rules a system was in violation of, not the individual violations; one rule can carry several.
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.