Class A Water Companies:
More than 10,000 service connections
- California American Water
- Coronado (HQ); Service Areas: Los Angeles, Monterey, Placer, Sacramento, San Diego, Sonoma, Ventura and Yolo Counties)
- California Water Service Company San Jose (HQ); Service Areas/Districts: Antelope Valley, East Los Angeles, Rancho Dominguez, Westlake, (Los Angeles County); Bakersfield, Kern River Valley (Kern County); Bayshore, Bear Gulch (San Mateo County); Chico, Oroville (Butte County); Dixon (Solano County); King City, Salinas (Monterey County); Livermore (Alameda County); Los Altos (Santa Clara County); Marysville (Yuba County); Redwood Valley (Sonoma and Lake Counties); Selma (Fresno County); Visalia (Tulare County); Stockton (San Joaquin); Willows (Glenn County)
- Golden State Water Company San Dimas (Contra Costa, Imperial, Lake, Los Angeles, Orange, Sacramento, San Bernardino, San Luis Obispo, Santa Barbara and Ventura Counties)
- Great Oaks Water Company San Jose (Santa Clara County)
- Liberty Utilities Apple Valley (San Bernardino County) and Downey (Los Angeles County)
- San Gabriel Valley Water Company El Monte (Los Angeles and San Bernardino Counties)
- San Jose Water Company San Jose (Santa Clara County)
- Suburban Water Systems Covina (Los Angeles and Orange Counties)
Class B Water Companies:
2,000-10,000 service connections
- Alco Water Service Salinas (Monterey County)
- Bakman Water Company Fresno (Fresno County)
- Del Oro Water Co., Inc. Chico (Butte and Tuolumne Counties)
- East Pasadena Water Company Pasadena (Los Angeles County)
- Fruitridge Vista Water Company Sacramento (Sacramento County)
Class C Water Companies:
500-2,000 Service Connections
- Agate Bay Water Company Carmichael (Placer County) (Agate Bay, northwest shore of Lake Tahoe)
- Bass Lake Water Company Bass Lake (Madera County)
- Big Basin Water Co., Inc. Santa Cruz (Santa Cruz County)
- Catalina Water Division, Southern California Edison Company Santa Catalina Island (Los Angeles County)
- Erskine Creek Water Company Lake Isabella (Kern County)
- Fulton Water Company Tahoe City (Placer County)
- Graeagle Water Company, Inc. Graeagle (Plumas County)
- Hillview Water Company Oakhurst (Madera County)
- Little Bear Water Company King City (Monterey County)
- Lukins Brothers Water Company South Lake Tahoe (El Dorado County)
- Meadowbrook Water Co. of Merced, Inc. Merced (Merced County)
- Mesa-Crest Water Company La Canada (Los Angeles County)
- Nacimiento Water Company Bradley (San Luis Obispo County)
- North Gualala Water Works Gualala (Mendocino County)
- Penngrove Water Company Santa Rosa (Sonoma County)
- Rio Plaza Water Company, Inc. Moorepark (Ventura County)
- Rogina Water Company, Inc. Talmage (Mendocino County)
- Rural Water, Inc. Grover Beach (San Luis Obispo County)
- Sea Ranch Water Company The Sea Ranch (Sonoma County)
- Searles Domestic Water Company Trona (San Bernardino County)
- Southern California Edison Company Santa Catilina Island (Los Angeles County)
- Tahoe Cedars Water Company Tahoma (El Dorado and Placer Counties)
- Tahoe Park Water Company, Inc. Tahoe City (Placer County)
- Yosemite Spring Park Utility Co. Coarsegold (Madera County)
Class D Water Companies:
Less than 500 Service Connections
- Alpine Village Water Company Porterville (Tulare County)
- Arroyo Center Water Co., Inc. Greenfield (Monterey County)
- Baycliff Subdivision Lower Lake (Lake County)
- Beasore Meadows Water System Oakhurst (Madera County)
- Benbow Water Corporation Garberville (Humboldt County)
- Black Butte Water Co. Orland (Glenn County)
- California Hot Springs Water Serv. California Hot Springs (Tulare County)
- Canada Woods Water Company Salinas (Monterey County)
- Casmite Corporation Casmalia Subdivision (Santa Barbara County)
- Cazadero Water Company Cazadero (Sonoma County)
- Central Camp Water Inc. Friant (Madera County)
- Cobb Mountain Water Company Cobb (Lake County)
- Cold Springs Water Company, Inc. Cold Springs (Tuolumne County)
- Cottage Springs Water Company Avery (Calaveras County)
- Dunnigan Water Works Dunnigan (Yolo County)
- Easton Estates Water Company Fresno (Fresno County)
- Foothill Ditch Company Exeter (Tulare County)
- Geyserville Water Works Geyserville (Sonoma County)
- Goodyears Bar Water Company Sacramento (Sierra County)
- Hat Creek Water Company Old Station (Shasta County)
- Havasu Water Company, Inc. Havasu Landing (San Bernardino County)
- Idylwild Water System Los Gatos (Santa Clara County)
- Interstate 5 Utility Company, Inc. Bakersfield (Kern County)
- January Water Company Tulare (Tulare County)
- Keene Water System Keene, Woodford (Kern County)
- Kenwood Village Water Company Santa Rosa (Sonoma County)
- Lake Alpine Water Company, Inc. Bear Valley (Alpine County)
- Lakeview Water Company Havasu Landing (San Bernardino County)
- Larkspur Meadows Water Company Paramount (Tehama County)
- Las Flores Water Works Gerber (Tehama County)
- Lewiston Valley Water Co., Inc. Lewiston (Trinity County)
- Little Bear Water, Inc. King City (Monterey County)
- Live Oak Springs Water and Power Co. Boulevard (San Diego County)
- Llano Del Rio Water Company Llano (Los Angeles County)
- Long Canyon Water Company Bakersfield (Kern County)
- Lytle Springs Water Company Lytle Creek (San Bernardino County)
- MacDoel Water Works Klamath Falls (Siskiyou County)
- Madden Creek Water Company Tahoma (Placer County)
- Meadow Valley Water Works Meadow Valley (Plumas County)
- Mecchi Water Company San Jose (Santa Clara County)
- Meyers Water Company Napa (Napa County)
- MHC Aquisition One, LLC Chicago (Santa Cruz County)
- Mira Monte Water Company Gerber (Tehama County)
- Mountain Mesa Water Company Bakersfield (Kern County)
- Owens Valley Water Company Los Angeles (Inyo County)
- Pierpoint Springs Resort Water Co. Camp Nelson (Tulare County)
- Pinon Hill Water Company Tehachapi (Kern County)
- Point Arena Water Works, Inc. Point Arena (Mendocino County)
- Ponderosa Sky Ranch Water System Paynes Creek (Tehama County)
- PureSource Water, Inc. Aptos (Santa Cruz County)
- R.R. Lewis Small Water Company Stockton (Sierra County)
- Ramona Water Company Palm Desert (Riverside County)
- Redwood Lodge Water Company Los Gatos (Santa Cruz County)
- Riverview Estates Water Company Red Bluff (Tahama County)
- Rolling Green Utilities, Inc. Big Pine (Inyo County)
- Sequoia Crest, Inc. Springville (Tulare County)
- Sereno Del Mar Water Company Sereno Del Mar (Sonoma County)
- Sierra City Water Works, Inc. Sierra City (Sierra County)
- Slide Inn/Snobowl Water Company Sonora (Tuolumne County)
- Sonoma Springs Water Company, LLC Kenwood (Sonoma County)
- Sonora Water Company Sonora (Tuolumne County)
- Spreckels Water Company Spreckels (Monterey County)
- Spring Crest Water and Power Company Mountain Center (Riverside County)
- Stone Creek Water, Inc. Stone Creek (Riverside County)
- Susan River Park Water Company Susanville (Lassen County)
- Tahoe Swiss Village Utilities, Inc. Homewood (El Dorado and Placer Counties)
- Timberland Water Service Tahoe City (Placer County)
- Traver Water Company Coalinga (Tulare County)
- Trinity Village Water Company Eureka (Trinity County)
- Twin Lakes Enterprises Bridgeport (Mono County)
- Twin Valley Water Company, Inc. Morgan Hill (Santa Clara County)
- Vista Grande Water System Gerber (Tehama County)
- Warring Water Service, Inc. Piru (Ventura County)
- Weimar Water Company, Inc. Weimar (Placer County)
- Wendell Water Company Santa Rosa (Sonoma County)
- West San Martin Water Works, Inc. San Martin (Santa Clara County)
- West Water Company Cloverdale (Sonoma County)
- Yerba Buena Water Company Thousand Oaks (Ventura County)
- Yermo Water Company Yermo (San Bernardino County)
