California Water Service - San Carlos, CA Water Quality
What's in California Water Service - San Carlos's water?
California Water Service - San Carlos has a health-based violation on record, but none in the last five years - an older issue, not necessarily a current one. It serves 35,344 people through 10,474 service connections.
How this compares nationally
California Water Service - San Carlos has 4 violations on record in total, 4 of them health-based - ranking it 4,588th of 12,903 systems by violation count, the 64th percentile nationally.
How California Water Service - San Carlos compares within CA
Among the 804 CA systems in this dataset, the average is 5.8 health-based violations - California Water Service - San Carlos's 4 is at or below that. See the lead and copper guide for why lead counts differently.
Most recent violation on record
The last violation EPA has on record for California Water Service - San Carlos is from 2015-01-03 (health-based: 2015-01-03). Last reported to EPA: 06/22/2026.
What kind of problem, specifically
California Water Service - San Carlos's flagged contaminants and rule violations, grouped by what they actually mean for a filter choice rather than left as EPA's raw code list:
- Microbial contamination / treatment technique - flagged from: Coliform (TCR); Surface Water Treatment Rule
The most severe category on record is microbial contamination / treatment technique, which points toward a microbial-class filter if you want to address it directly.
What this data is and is not
California Water Service - San Carlos's numbers here come from its own required reporting to EPA under the Safe Drinking Water Act, not from an independent test of your glass of water. This record - 4 health-based violations on file for California Water Service - San Carlos - stops at the meter and cannot see household plumbing on the other side of it. The guide to what this data misses covers that gap.