Tapcensus

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.

Active systems 172 72 community systems
People served 293K by public water systems
Systems with violations 54 31% of active systems, past 3 years
Serious violators 0 9 systems carry a health flag

Needs attention

Green River Mutual Water Co. CA4000554 · Community water system · Serves 350 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Sycamore Mineral Springs Resort CA4000689 · Non-Transient non-community system · Serves 200 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Vachell Water System CA4000806 · Non-Transient non-community system · Serves 150 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Madonna Inn Water Company CA4000780 · Non-Transient non-community system · Serves 120 3 rules violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Halcyon Water System CA4000501 · Community water system · Serves 110 3 rules violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Elks Lodge #322 CA4000671 · Non-Transient non-community system · Serves 40 3 rules violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Sheridan Road Mutual Water Association CA4000623 · Non-Transient non-community system · Serves 38 1 rule violated in the past three years. Unresolved: Lead and Copper Rule Revisions.
Higuera Apartments CA4000563 · Community water system · Serves 30 3 rules violated in the past three years. Unresolved: Lead and Copper Rule and Lead and Copper Rule Revisions.
Cuyama Lane Water Company CA4000598 · Non-Transient non-community system · Serves 25 3 rules violated in the past three years. Unresolved: Lead and Copper Rule Revisions.

Community water systems

72 systems, largest first
SystemServesStatusRules violated, 3 yrUnresolved
San Luis Obispo Water Department
 49,534 0 0
Atascadero Mutual Water CO
 33,307 0 0
City of Paso Robles Water Division
 31,176 0 0
City of Arroyo Grande Utilities Division
 17,963 1 0
California Mens Colony
 15,000 0 0
Nipomo Comm Services Dist
 13,771 0 0
City of Grover Beach Public Works Dept
 12,701 0 0
Morro Bay PW Dept Water Division
 10,757 0 0
Templeton Csd
 8,041 0 0
Pismo Beach Water Department
 7,944 2 0
Oceano Comm Services Dist.
 7,598 0 0
Los Osos Community Services District
 7,086 0 0
Cambria Comm Services Dist
 6,038 0 0
Golden State Water Company los Osos
 5,942 0 0
Golden State Water Company Nipomo
 4,512 0 0
Woodlands Development
 3,862 0 0
San Miguel Community Services District
 3,019 0 0
Heritage Ranch Csd
 2,956 1 0
Cayucos Beach Mutual Water Company
 2,567 0 0
Nacimiento Water Company
 2,191 3 2
Morro Rock Mutual Water CO
 2,181 0 0
Golden State Water Company-Cypress Ridge
 2,032 0 0
Avila Beach Community Services District
 1,630 0 0
San Miguelito Mwc
 1,600 1 0
Golden State Water Company Edna
 1,495 0 0
Slo Cwwd No. 23 Santa Margarita
 1,291 0 0
Slocsa #10a Cayucos
 1,200 0 0
Atascadero State Hospital
 1,100 1 0
Slo Csa No. 16 Shandon
 1,085 0 0
Mesa Dunes Mobile Home Estates
 600 0 0
S & T Mutual Water Company
 591 0 0
Woodland Park Mutual Water CO
 538 2 0
Walnut Hills Mutual Water CO
 486 0 0
San Simeon Csd
 462 1 0
Garden Farms C.w.d.
 440 1 1
Los Robles Mobile Home Estates
 420 0 0
Green River Mutual Water Co.
 350 1 1
Santa Ysabel Ranch Mwc
 344 0 0
Rancho Colina Mobile Home Park
 252 1 0
Gran Cielo Mutual Water Company
San Simeon 		139 0 0
Irish Hills Mutual Water CO
 135 0 0
Canyon Crest Mutual Benefit WC
 133 0 0
Edna Valley Ranch East
 132 0 0
Spanish Lakes Mutual Water CO
 125 0 0
Callender Grove Mutual Water
 116 1 0
Halcyon Water System
 110 3 1
Las Ventanas Ranch
 108 0 0
Varian Ranch Mutual Water
 105 0 0
Resthaven Mobile Home Park
 99 1 0
Afuera de Chorro Water Company
 85 1 0
Non-community systems (100: schools, campgrounds, workplaces, restaurants)

These systems serve places people visit rather than homes.

SystemServesStatusRules violated, 3 yrUnresolved
Brecon Estate
San Simeon 		9,012 0 0
Grosso Kresser Winery
San Simeon 		3,606 0 0
Tiger Water Supply
 1,600 0 0
Caltrans Shandon Rest Stop
 1,300 1 0
Pg&e
 1,200 1 1
Montana de Oro State Park
 990 1 0
Coastal Christian School
 650 0 0
Hearst Memorial State Beach
 500 0 0
The Anderson
Cayucos 		500 0 0
Vines R.v. Resort
 400 0 0
Fiero Lane Water Company, Inc.
 324 0 0
Branch Elementary School
 253 0 0
Cal Shasta Club
 240 0 0
Hearst Monument State Park
 215 0 0
Parrish Family Winery
 207 0 0
Jack Ready Imagination Park
Cayucos 		200 0 0
Octagon Barn Center Association
 200 0 0
Strasbaugh, INC
 200 1 0
Sycamore Mineral Springs Resort
 200 1 1
Opolo Water System
San Simeon 		150 0 0
Santa Margarita Recreation Area
 150 0 0
Vachell Water System
 150 1 1
Christmas Cove
 132 0 0
San Simeon Estate Winery
San Simeon 		132 0 0
Calipaso Winery
Cayucos 		130 0 0
J Lohr Winery
 125 0 0
Port San Luis Harbor District
 125 0 0
Madonna Inn Water Company
 120 3 1
Paso Robles RV Ranch
 105 1 0
Creston Elementary School
 100 0 0
Lopez Recreation Area
 100 0 0
Noll Properties
 100 0 0
Pleasant Valley Elementary
 100 1 0
Ragged Point Inn
 100 1 0
LE Cuvier Winery
Cayucos 		92 0 0
Greenheart Farms
 91 0 0
Talley Farms Labor Housing
 90 0 0
Tri Counties Club
 87 2 0
Zoo Med-Winterhaven
Cayucos 		80 1 0
Center of Effort Winery
 75 0 0
Usasa-Pom Enclave Camp Roberts
 75 0 0
Santa Margarita KOA
 70 0 0
Paso 360
 65 0 0
Laetitia Vineyard & Winery INC
 62 0 0
Santa Margarita Ranch Headquarters
Cayucos 		62 0 0
Ball Tagawa Growers
 60 0 0
Toyota San Luis Obispo
 57 0 0
Booker Winery
Cayucos 		56 0 0
Carpenter Winery
Cayucos 		54 0 0
Mt. Olive Organic Farm
Cayucos 		51 0 0
Granite Ridge
 50 0 0
Hunter Ranch Golf Course
 50 0 0
Laguna Vista Boat Club
 50 0 0
Northshore S & B, INC
 50 0 0
Paragon Triangle Water Supply
 50 0 0
Tank Farm Business Park
 45 2 1
Carrisa Plains Elementary
 40 1 0
Chamisal Vineyards
Cayucos 		40 0 0
Elks Lodge #322
 40 3 1
Slo Partners
 40 1 1
Speedling, INC
 40 0 0
Halter Ranch
 39 0 0
Jada Vineyard and Winery
San Simeon 		39 0 0
Sheridan Road Mutual Water Association
 38 1 1
Guadalupe Cooling Company
 35 1 0
Parsons Water Supply
 35 0 0
Playa Dulce
 35 0 0
Waste Connections Water CO
 35 1 0
J M Sims Water Supply
 34 0 0
Horizon Lane Water Supply
 32 0 0
Caelesta Winery
Cayucos 		30 0 0
Cerro Alto Campground
 30 1 0
Edna Valley Vineyards
 30 0 0
Holdgrafer & Associates
 30 0 0
Laureate Water Company
 30 1 0
Longbranch Saloon, the
 30 0 0
Adelaida Vineyards & Winery
San Simeon 		27 1 0
Biddle Regional County Park
 27 0 0
Harmony Water Works
 27 0 0
Daou Vineyards, LLC
 26 0 0
Pacific Dunes Ranch
 26 0 0
Sutter Home Winery Inc. Trinchero CC
 26 0 0
141 Suburban Road Water Supply
 25 1 0
Aronhill Vineyard
 25 0 0
Babe Ruth's Oak View
 25 0 0
Congregation Beth David
 25 0 0
Creston Country Store
 25 1 0
Cuyama Lane Water Company
 25 3 1
Halfway Station
 25 1 0
Independence Water System
 25 0 0
Loading Chute
 25 1 0
Niner Wine Estates, LLC
 25 0 0
Paso Robles Chevrolet Cadillac
 25 0 0
Precision Mutual Water Company
 25 1 0
San Paso Truck Stop
 25 1 0
Sixmilebridge Winery
 25 0 0
Sunset Drive-In Snack Bar
 25 0 0
Tmc Suburban, LLC
 25 0 0
County of Monterey-Lake Nacimiento
 20 0 0
Rinconada Trailer Park
 10 0 0
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.