Tapcensus

Water quality in Diamond Bar, California

Diamond Bar is in Los Angeles County. 271 active public water systems serve the county; 66 had an EPA violation in the past three years.

Most likely your provider

Walnut Valley Water District CA1910234 · Community water system · Surface water purchased
Serves 100,941 people Rules violated, past 3 years 0 Last sanitary survey Jun 27, 2023 Distance 1.1 mi

Your location is within the outer bounds of this system's EPA service area.

View system details EPA facility report

Other community water systems in Los Angeles County

198 systems, nearest first
SystemServesStatusRules violated, 3 yrDistance
Calif State Polytechnical Univ Pomona
 2,668 2 3.8 mi
Three Valleys Mwd
 0 0 3.9 mi
Valencia Heights Water Co.
 7,775 0 5.0 mi
Pomona City, Water Dept.
Pomona		 151,713 0 5.1 mi
Rowland Water District
 56,100 0 5.4 mi
Suburban Water Systems-Covina Knolls
 1,451 0 5.8 mi
Covina Valley Water Company Wholesale
 0 0 6.6 mi
Suburban Water Systems-San Jose
 170,523 0 6.6 mi
Gswc-San Dimas
 56,564 0 6.7 mi
Covina-City, Water Dept.
Covina		 33,300 0 6.8 mi
LA Puente Valley Cwd
 8,276 0 7.7 mi
LA Habra Heights Cwd
 5,682 0 8.2 mi
Metropolitan Water Dist. of So. Cal.
 0 0 8.4 mi
City of Industry Waterworks Systems
La Puente		 6,151 0 8.8 mi
Suburban Water Systems-Glendora
 5,301 0 8.9 mi
LA Verne, City WD
La Verne		 31,334 0 9.3 mi
Glendora-City, Water Dept.
Glendora		 44,411 0 9.4 mi
Azusa Light and Water
 110,044 0 9.6 mi
Gswc Claremont
 39,776 0 9.7 mi
Valley County Water Dist.
 68,871 0 10.5 mi
California Domestic Water Company
 0 0 10.5 mi
Valley View Mutual Water Co.
 4,613 0 11.0 mi
Suburban Water Systems-Whittier
 66,565 0 11.6 mi
San Gabriel Valley Water Co.-El Monte
 240,000 0 12.2 mi
Del Rio Mutual
 700 1 12.2 mi
All 199 community water systems in Los Angeles County
Non-community systems in Los Angeles County (72: schools, campgrounds, workplaces, restaurants)

These systems serve places you visit rather than homes.

SystemServesStatusRules violated, 3 yrUnresolved
Irwindale Brewery Yard (iby)
 300 0 0
Martin Marietta Southern Calif Aggregate
 51 0 0
Usfs-Chantry Flats-A16 Water
 113 0 0
Coldbrook Campground
 38 0 0
Plant Water Well Rockview Dairy
South Gate 		45 0 0
Rancho los Amigos Hospital
 3,200 0 0
Henninger Flats
 50 0 0
Usfs-Skyline Park / Mount Wilson A-4
 25 0 0
Usfs-Crystal Lake B-13 Water
 2,000 0 0
Usfs-Red Box Station A-3
 25 0 0
Young-Nak Presbyterian Church
 25 0 0
Millard Canyon Improvement Association
 42 1 0
Usfs-Chilao Main A-9
 50 0 0
Angeles Crest Christian Camp
 112 1 0
Colby Ranch-United Methodist Camp
 180 0 0
Mount Kare Camp/kare Youth League
 59 0 0
Usfs-Big Pines V-2
 54 0 0
Mountain High East Ski Area
 150 0 0
Clear Creek Outdoor Education Center
 105 0 0
Huttopia Paradise Springs
 302 1 0
Usfs-Jackson Lake V-4
 805 0 0
Usfs-Appletree Flats V-3
 25 0 0
Camp Elk
 121 0 0
Usfs-Monte Cristo Camp T-4
 116 0 0
Usfs-Valyermo Ranger Station
 25 1 1
Saint Andrews Abbey
 210 1 1
Rancho Ybarra Christian Camp
 73 0 0
Angeles Shooting Ranges
 490 0 0
1000 Trails / Soledad Canyon Preserve
 812 1 0
Acton Four Square Church
 50 0 0
Acton-Agua Dulce Lds Church
 150 0 0
Acton la North KOA
 400 0 0
General Atomics Aeronautical Gray Butt
 405 0 0
Acton Conservation Camp #11
 90 4 0
Desert Aire Golf Course
 80 0 0
Vasquez Rocks County Park
 30 0 0
Los Angeles World Airports
 180 0 0
Ilead Agua Dulce Charter School
 450 1 1
Agua Dulce Women's Club
 50 0 0
Lang Ranch Shopping Center
 28 0 0
Wagon Wheel Plaza
 55 1 0
Agua Dulce Water System
 493 0 0
Antelope Valley Indian Museum State Park
 506 0 0
Agua Dulce Winery
 113 0 0
Lockheed Martin Skunk Works
 135 0 0
Living Springs Church
 50 0 0
Shepherd of the Hills
 80 0 0
Northrop Grumman Corp.
 5,764 1 0
LE Chene Restaurant Water System
 100 0 0
Lancaster National Soccer Center
Lancaster 		500 0 0
All non-community systems
About this data

Water systems are matched to Los Angeles County, nearest to Diamond Bar 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.

Town locations and ZIP code areas come from U.S. Census Bureau 2020 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.