Ontario Municipal Utilities Company
EPA ID: CA3610034 · 185,010 people served · 9 ZIP codes
Across every monitored period in the past five years, Ontario Municipal Utilities Company reported no EPA violations for its service population of 185,010.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for Ontario Municipal Utilities Company Source: EPA SDWIS service area boundaries.
Service area boundary — Grade B
Service Area Demographics
The Ontario Municipal Utilities Company serves a community with a median household income of $82,294 and an estimated 354,794 residents across its service area. Approximately 67% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
Environmental Justice Note: 51% of the population in this service area is classified as disadvantaged under EPA's EJScreen criteria. Communities with higher disadvantaged populations often face disproportionate environmental and health burdens, including aging water infrastructure and limited resources for remediation.
🌊 Where Does Your Water Come From?
Ontario Municipal Utilities Company's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 1% of homes in San Bernardino County, California rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 60th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 34 detections recorded. 9 exceed federal EPA limits (4 ppt for PFOA/PFOS). 5 exceed state limits.
Comparable Water Systems
Similar-sized systems in California
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
ONTARIO MUNICIPAL UTILITIES COMPANY (EPA ID: CA3610034) is a community water system in California that serves approximately 185,010 people from surface water sources.
This system provides water to 9 ZIP codes across 5 communities.
Average Home Safety Score: B (77/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 91758 | 0.0006 mg/L | No | N/A |
| 91761 | 0.0006 mg/L | No | N/A |
| 91762 | 0.0006 mg/L | No | N/A |
| 91764 | 0.0006 mg/L | No | N/A |
| 91798 | 0.0006 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: 6 ZIP codes confirmed via EPA Community Water System Service Area Boundaries v3 plus 3 additional ZIPs inferred from SDWIS registry data. The EPA-confirmed set is the most reliable; SDWIS-inferred entries may be narrower than the real deployment area.
- 91710 — Chino
- 91743 — Guasti
- 91758 — Ontario
- 91761 — Ontario
- 91762 — Ontario
- 91763 — Montclair
- 91764 — Ontario
- 91786 — Upland
- 91798 — Ontario
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Ontario Municipal Utilities Company (CA3610034) on EPA.gov.
Frequently Asked Questions
Is Ontario Municipal Utilities Company water safe to drink?
Based on EPA records, Ontario Municipal Utilities Company has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Ontario Municipal Utilities Company serve?
Ontario Municipal Utilities Company serves approximately 185,010 people across 9 ZIP codes in California.
Where does Ontario Municipal Utilities Company get its water?
The primary water source is surface water.
Federal UCMR5 PFAS Monitoring: Above Current MCL
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). One or more PFAS compounds were measured above the current state-enforceable MCL.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.