What's in CALIFORNIA WATER SERVICE - SAN MATEO's water?
CALIFORNIA WATER SERVICE - SAN MATEO has a health-based violation on record, but none in the last five years - an older issue, not necessarily a current one. Population served: 102,348, over 25,440 connections.
How this compares nationally
CALIFORNIA WATER SERVICE - SAN MATEO has 3 violations on record in total, 2 of thems health-based - ranking it 6,983th of 12,903 systems by violation count, the 46th percentile nationally.
How CALIFORNIA WATER SERVICE - SAN MATEO compares within CA
CA's 803 covered systems average 5.8 health-based violations each; CALIFORNIA WATER SERVICE - SAN MATEO carries 2, not more than typical for the state. 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 MATEO is from 1993-01-06 (health-based: 1993-01-06). Last reported to EPA: 06/22/2026.
What kind of problem, specifically
CALIFORNIA WATER SERVICE - SAN MATEO'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 MATEO'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. Between the utility's meter and CALIFORNIA WATER SERVICE - SAN MATEO's customers' taps is household plumbing, invisible to a system-level record ranked 6,983th of 12,903 by violation count. The guide to what this data misses covers that gap.