States → California
State profile · EPA SDWIS + UCMR5
California Drinking Water Quality
7,249 public water systems serve 42,404,883 people across California, with every Safe Drinking Water Act violation and UCMR5 PFAS result on record.
- 7,249
- Water systems
- 153,308
- Total violations
- 89.2%
- Systems w/ a violation
- 64.4%
- PFAS detection rate
The verdict
Across California, 6,464 of 7,249 water systems (89.2%) carry at least one EPA violation, and 447 of 694 UCMR5-tested systems show PFAS.
- 153,308
- Total EPA violations on record
- 42%
- Health-based (MCL / treatment)
- 89.2%
- Systems with ≥1 violation
- 64.4%
- UCMR5 PFAS detection rate
Water Systems
7,249
Total Violations
153,308
Violation Rate
89.2%
PFAS Detection
64.4%
447 of 694 tested
Violation Composition
How California's 153,308 violations break down by type, per EPA SDWIS classification.
Health-based (63,983) Monitoring/Reporting (89,325)
| Metric | Value | Share |
|---|---|---|
| Public water systems | 7,249 | - |
| Population served | 42,404,883 | - |
| Total violations | 153,308 | 100% |
| Health-based violations | 63,983 | 41.7% |
| Systems with violations | 6,464 | 89.2% |
| PFAS detection rate | 447 of 694 | 64.4% |
Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement. Monitoring/reporting violations indicate procedural issues (missed tests, late reports) - not necessarily a contamination event.
Largest Water Systems
Los Angeles-City, Dept. of Water & Power
Los Angeles, CA · 3,875,566 served
East Bay MUD
Oakland, CA · 1,442,800 served
San Diego, City Of
San Diego, CA · 1,385,379 served
San Jose Water
San Jose, CA · 1,039,920 served
Sfpuc City Distribution Division
Burlingame, CA · 848,019 served
Eastern Municipal WD
Perris, CA · 666,581 served
City of Fresno
Fresno, CA · 545,716 served
City of Sacramento Main
Sacramento, CA · 520,407 served
Long Beach Utilities Department
Long Beach, CA · 466,772 served
Irvine Ranch Water District
Irvine, CA · 444,800 served
City of Anaheim
Anaheim, CA · 348,593 served
Alameda County Water District
Fremont, CA · 344,000 served
City of Santa Ana
Santa Ana, CA · 310,539 served
Riverside, City Of
Riverside, CA · 298,398 served
Santa Clarita Valley Water Agency
Newhall, CA · 294,090 served
Gswc - Southwest
Hawthorne, CA · 277,740 served
Helix Water District
La Mesa, CA · 277,668 served
Coachella Vwd: Cove Community
Palm Desert, CA · 270,000 served
Cws - Bakersfield
San Jose, CA · 267,881 served
San Gabriel Valley Water Co.-El Monte
El Monte, CA · 248,000 served
Most Violations
#1 Rohnert Park, City Of Rohnert Park
561 #2 Hanford, City Of Hanford
454 #3 Land Projects Mutual Water Co. Lancaster
426 #4 Encinal RD WS #01 Salinas
395 #5 John Hovannisian Water System Fresno
378 #6 Riverside CSA #122-Mesa Verde Blythe
364 #7 Campers Inn - RV & Golf Course Dunnigan
355 #8 Harris Farms Headquarters Coalinga
343 #9 Cypress Canyon Water System Lake Isabella
340 #10 Arvin Community Services Dist Arvin
331 #11 Pappas & Co (Mendota) Fresno
310 #12 Washington School WS Salinas
310 #13 Moro RD WS #09 Salinas
298 #14 Armona Community Services Dist Armona
292 #15 Nps-Wolverton Three Rivers
278 Counties in California
Los Angeles
276 systems · 10,109,089 served
· 3,972 violations
San Diego
197 systems · 3,744,323 served
· 4,832 violations
Orange
46 systems · 3,201,893 served
· 507 violations
Riverside
201 systems · 2,839,125 served
· 6,103 violations
San Bernardino
318 systems · 2,830,626 served
· 4,611 violations
Alameda
27 systems · 2,249,634 served
· 275 violations
Santa Clara
119 systems · 2,097,044 served
· 2,640 violations
Sacramento
166 systems · 1,685,812 served
· 2,206 violations
Fresno
340 systems · 1,053,609 served
· 11,624 violations
San Francisco
8 systems · 1,040,304 served
· 77 violations
Kern
341 systems · 1,032,343 served
· 11,890 violations
Ventura
95 systems · 882,799 served
· 1,507 violations
San Mateo
52 systems · 782,067 served
· 1,318 violations
San Joaquin
310 systems · 775,760 served
· 5,057 violations
Contra Costa
86 systems · 565,242 served
· 1,010 violations
Stanislaus
195 systems · 511,603 served
· 3,426 violations
Santa Barbara
152 systems · 490,541 served
· 2,187 violations
Sonoma
440 systems · 481,120 served
· 6,052 violations
Monterey
315 systems · 476,400 served
· 13,641 violations
Solano
61 systems · 470,297 served
· 530 violations
Tulare
296 systems · 446,656 served
· 12,135 violations
Placer
123 systems · 429,603 served
· 1,542 violations
San Luis Obispo
167 systems · 347,560 served
· 1,652 violations
El Dorado
129 systems · 294,812 served
· 3,192 violations
Marin
49 systems · 285,765 served
· 805 violations
Santa Cruz
96 systems · 274,174 served
· 2,563 violations
Merced
119 systems · 267,234 served
· 1,403 violations
Yolo
90 systems · 260,218 served
· 2,443 violations
Butte
88 systems · 231,825 served
· 1,512 violations
Shasta
180 systems · 211,056 served
· 2,130 violations
Showing top 30 of 58 counties.
Drinking Water Guides
Frequently Asked Questions
How many water systems are in California? ▼
California has 7,249 public water systems serving approximately 42,404,883 people. These include community water systems, non-transient non-community systems, and transient non-community systems regulated under the Safe Drinking Water Act.
How many drinking water violations are in California? ▼
California has 153,308 total drinking water violations on record, with 63,983 classified as health-based violations. 89.2% of water systems in the state have at least one violation.
Has PFAS been found in California drinking water? ▼
Of 694 water systems tested for PFAS in California, 447 had PFAS detected, a 64.4% detection rate. PFAS are persistent "forever chemicals" that do not break down in the environment.
What is the violation rate for California water systems? ▼
California's violation rate is 89.2%. This measures the percentage of public water systems that have at least one recorded violation in the EPA SDWIS database, including both health-based and monitoring/reporting violations.
Where does this California water data come from? ▼
All drinking water data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS is the federal database that tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources & Methodology
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.