Ontario, California Tap Water Quality
Free EPA data for 4 community water systems serving 185,170+ residents. Click any system to see violations, lead test results, and a safety grade.
🔍 Not sure which system serves your address?
Enter your ZIP code to find your exact water provider →Ontario Drinking Water: Frequently Asked Questions
Is Ontario, California tap water safe to drink?
Ontario has 4 community water systems regulated by the EPA. Each system is required to test regularly for hundreds of contaminants and publicly report any violations. Click any water system listed above to see its specific violation history, lead test results, and a plain-English safety grade.
How many water utilities serve Ontario, California?
4 community water systems serve Ontario, California, providing water to approximately 185,170 people. Different neighborhoods may be served by different utilities. Enter your ZIP code at the top to find your specific provider.
Does Ontario tap water have lead?
Lead in drinking water typically enters from old pipes and fixtures inside homes and buildings, not from the treatment plant. The EPA requires water systems to monitor for lead under the Lead and Copper Rule. Click any water system above to see its most recent 90th-percentile lead test results. Homes built before 1986 are most likely to have lead plumbing components.
What contaminants have been found in Ontario drinking water?
EPA violation records for Ontario water systems are listed on each utility's report page. Common regulated contaminants include disinfection byproducts (TTHMs, HAA5), coliform bacteria, nitrates, and lead. Click any utility above to see its full violation history going back 10 years.
How do I find out which water company serves my address in Ontario?
Enter your Ontario ZIP code in the search box at the top of this page. ClearWater will identify the specific water system serving your area and show you its EPA violation history, lead test results, and an overall safety grade. You can also check your water bill or your utility's annual Consumer Confidence Report (CCR).