City guide · ZIP / utility based
Ontario tap water quality
Ontario ZIPs typically map to municipal water. Nearby IE cities can share overlapping candidates — check your ZIP.
Honest framing: This is not a citywide water score. We match your ZIP to a public water system using CA service-area data where available. Contaminant lists are curated detections — non-detects are omitted. Educational only — not medical advice, not a faucet lab test, and not affiliated with EWG or any utility.
About 4 ZIP codes in our index are labeled Ontario (San Bernardino County). Pick an example below or enter your own ZIP.
Example ZIPs in Ontario
Utilities often matched near Ontario
Names come from public CA water-system records for ZIPs labeled Ontario. Your block may differ — always open the ZIP report.
- Ontario Municipal Utilities Company
- Gswc - Calipatria
Want the full drinking water report?
Open a ZIP report for curated detections vs EPA limits and CA health guidelines. Open report for 91758 →
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