Ontario
Is Ontario tap water safe to drink?
Mostly yes — Ontario scores 90/100. This report aggregates EPA drinking water data across 1 local system in Ontario. We found 9 total violations (5 unresolved).
Real-Time Environment
Live: 06:15 PM☀️ No active precipitation. Rainfall can impact surface water turbidity and pollutant runoff in Ontario.
Water Quality Impact
🛡️ Home Water Treatment Needs
Should you invest in filtration or softening for your home in Ontario?
Expert Advice
Your water quality is excellent. Standard filtration is optional but can further enhance taste.
Buying a Filter?
Should you buy a water purifier in Ontario? See our analysis.
Baby Formula Safety
Is Ontario tap water safe for infants? Critical safety guide.
Homebuyer's Perspective
For those looking to relocate to Ontario, water quality is a key factor in long-term property maintenance. The high safety score (90/100) suggests lower risk for plumbing corrosion and appliance scaling.
Health & Family Safety
Residents should monitor Lead (90th percentile) levels. Pregnant women and families with young children should consult the specific EPA health goals listed below.
View Health Risk Glossary →Compliance Record for Ontario
Based on EPA SDWIS violation records and contaminant test results for all water systems serving Ontario.
Frequently Asked Questions
Is Ontario tap water safe to drink?
Mostly yes — Ontario scores 90/100.
How many water systems serve Ontario?
Ontario is served by 1 public water system in our latest EPA-backed dataset.
How can I check water quality for my exact address in Ontario?
Use the WaterQ search tool to look up your ZIP code and view nearby systems, contaminant levels, and recent violations for Ontario.
What is the water quality score for Ontario?
The water quality score for Ontario is 90 out of 100, based on EPA contaminant data, violation history, and testing results across the 1 system serving the city.
What are the top contaminants in Ontario?
The top contaminants detected in Ontario include Lead (90th percentile). View detailed information on our contaminants page.
Ontario Water Quality Summary
Ontario, CA receives a water quality score of 90/100 (Grade A) based on EPA Safe Drinking Water Information System (SDWIS) compliance data for 1 public water system serving the area.
Ontario's water quality is above the national average, with strong compliance records and low contaminant levels. Residents generally receive clean, safe tap water that meets EPA standards.
Ontario's score of 90 is 1 point above the California state average of 89, and above the nationwide average of roughly 78/100 across all U.S. states.
For residents of Ontario, California, a centralized municipal system manages the drinking water supply, delivering highly rated quality to this mid-size city. Operating within the West Coast region means the local water supply is influenced by nearby large urban centers, Central Valley agricultural activity, and the surrounding varied geology. For prospective homebuyers, this unified management provides reassurance of reliable tap water safety despite the complex environmental and geological factors characteristic of the region.
Water quality data is sourced from the U.S. EPA SDWIS database and updated quarterly. Learn about our scoring methodology → Read our California water quality rankings report →
Key Contaminants
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Water Systems Serving Ontario (1)
Check Your Specific Address
Water quality can vary by neighborhood in Ontario.
Related
Quick compare in California
Compare Ontario water quality: View all states · Contaminant library · How we score water quality