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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Real EPA measurements of bacteria (coliform) for California water systems — Six-Year Review compliance samples 2012–2019 (historical). Methodology
EPA does not publish per-city bacteria (coliform) measurements for California in the datasets we use, so this section shows what regulators actually recorded: every Safe Drinking Water Act violation tied to bacteria (coliform) at the 161 California public water systems we track, since 2016. Source: EPA SDWIS via ECHO (2026 Q2 extract).
16 of 161 tracked California systems logged 23 bacteria (coliform) violations since 2016; 2 were health-based (a limit or treatment requirement), the rest monitoring or reporting failures.
| System | Pop. served | Violations | Health-based | Latest | EPA record |
|---|---|---|---|---|---|
| Fullerton CITY OF FULLERTON | 139,461 | 1 | 1 | 2017-12-01 Maximum Contaminant Level Violation, E. coli (RTCR) | CA3010010 |
| Downey DOWNEY - CITY, WATER DEPT. | 110,556 | 1 | 1 | 2018-02-01 Treatment Technique, Level 2 Assessment (RTCR) | CA1910034 |
| San Diego SAN DIEGO, CITY OF | 1,385,379 | 5 | 0 | 2020-04-01 Monitoring, Routine (RTCR) | CA3710020 |
| Anaheim CITY OF ANAHEIM | 348,593 | 2 | 0 | 2022-10-01 Sample Siting Plan Errors (RTCR) | CA3010001 |
| Milpitas CITY OF MILPITAS | 81,773 | 2 | 0 | 2025-05-01 Monitoring, Routine (RTCR) | CA4310005 |
| Pico Rivera PICO RIVERA - CITY, WATER DEPT. | 40,600 | 2 | 0 | 2022-11-01 Monitoring, Routine (RTCR) | CA1910042 |
| San Jose SAN JOSE WATER | 1,039,920 | 1 | 0 | 2017-04-01 Monitoring, Source Water (GWR) | CA4310011 |
| Irvine IRVINE RANCH WATER DISTRICT | 444,800 | 1 | 0 | 2020-09-01 Monitoring, Routine (RTCR) | CA3010092 |
| Santa Ana CITY OF SANTA ANA | 310,539 | 1 | 0 | 2021-10-01 Sample Siting Plan Errors (RTCR) | CA3010038 |
| Burbank BURBANK-CITY, WATER DEPT. | 105,603 | 1 | 0 | 2022-09-01 Monitoring, Routine (RTCR) | CA1910179 |
| Baldwin Park VALLEY COUNTY WATER DIST. | 68,871 | 1 | 0 | 2019-08-01 Monitoring, Routine (RTCR) | CA1910009 |
| Rosemead CAL AMERICAN WATER CO | 66,809 | 1 | 0 | 2022-10-01 Monitoring, Routine (RTCR) | CA5610040 |
| Tustin CITY OF TUSTIN | 66,600 | 1 | 0 | 2016-07-29 Monitoring, Source Water (GWR) | CA3010046 |
| Madera CITY OF MADERA | 66,560 | 1 | 0 | 2017-07-06 Monitoring, Source Water (GWR) | CA2010002 |
| Arcadia CITY OF ARCADIA | 51,361 | 1 | 0 | 2016-01-01 Monitoring, Routine Minor (TCR) | CA1910003 |
| Carmichael CARMICHAEL WATER DISTRICT | 41,193 | 1 | 0 | 2025-07-01 Monitoring, Routine (RTCR) | CA3410004 |
Every California system with a bacteria (coliform) result in EPA's data, sorted by level. Averages of 2012–2019 finished-water samples, non-detects counted as zero — historical, not today's tap.
No bacteria (coliform) detections have been reported in California cities.
Coliform bacteria indicate potential fecal contamination. E. coli can cause severe gastrointestinal illness including bloody diarrhea, vomiting, and kidney failure. Other waterborne pathogens cause cholera, typhoid, hepatitis A, and giardiasis. Young children, elderly, and immunocompromised individuals face the greatest risk for severe outcomes.
Human and animal fecal waste; sewage treatment plant discharges; septic system failures
Based on our analysis of EPA Safe Drinking Water Information System (SDWIS) data and local water utility reports,bacteria (coliform) has been detected in 0 California water systems.
The EPA requires no more than 5% of samples test positive for coliform. Any E. coli positive triggers a violation. The EPA MCL for bacteria (coliform) is 0 presence/absence. This limit is set to protect public health based on available scientific evidence about the contaminant's health effects.
0 California cities have bacteria (coliform) detected in their water supply. All tested cities are within EPA safety limits.
Gastrointestinal illness, diarrhea, vomiting, potential kidney damage from E. coli. The most vulnerable groups include infants and young children and elderly.
The most effective methods for removing bacteria (coliform) include UV Disinfection, Reverse Osmosis, Ultrafiltration. Look for filters certified by NSF/ANSI for bacteria (coliform) reduction.
The EPA Maximum Contaminant Level (MCL) for bacteria (coliform) is 0 presence/absence.The EPA requires no more than 5% of samples test positive for coliform. Any E. coli positive triggers a violation.
This page shows what California utilities reported for bacteria (coliform). It cannot tell you what is coming out of your own tap: utility samples are taken across a whole system and averaged, levels vary by address and season, and anything picked up after the water leaves the main never appears in their report.
Home water test kitscheck your own tap before buying any filterRecommended filtration methods for bacteria (coliform) removal:
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Physical barrier to bacteria
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Paid links. We earn a commission if you buy, at no extra cost to you. Filters are matched to the removal methods listed above for bacteria (coliform).