Compliance figures for Ontario indicate average water quality in CA overall - some service areas have recorded health-based violations in recent monitoring cycles, while others operate cleanly, making system-level data the most actionable reference point for residents.

Data: EPA SDWIS

Overview

We track home safety data for 5 ZIP codes in Ontario, California (population ~181,574), covering 4 community water systems serving approximately 538,531 people region-wide. The EPA snapshots used for this build directly map water systems to 3 of 5 ZIP codes.

1 of 3 ZIP codes with a reported violation count in the available EPA record (33%) have recorded EPA violations. The available record reports no health-based violations for this measured scope.

Home Safety Score

Average Home Safety Score for Ontario: C (58/100)

Model 4.0.0 uses four measured components across three equally weighted domains. If a required domain is unavailable, no score is published:

Factor	What It Measures
Water Quality	EPA violations and compliance history
PFAS MCL Screen	UCMR 5 testing against the covered federal MCLs
Radon Risk	EPA radon zone classification
Annual AQI	EPA AirData county-year median with at least 90 observed days

Water Sources

Ontario water systems draw from: Surface water.

Lead & Copper

• Average lead level (90th percentile): 0.0007 mg/L (EPA action level: 0.015 mg/L)
• 0 of 3 ZIP codes with known status exceed the EPA lead action level

Radon Risk

Dominant radon zone: Zone 2 (Moderate Risk)

• Zone 1 (High): 0 ZIP codes
• Zone 2 (Moderate): 5 ZIP codes
• Zone 3 (Low): 0 ZIP codes

The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.

Top Contaminants

Areas with Most Violations

Areas with No Violations

All ZIP Codes in Ontario

• 91758
• 91761 [C]
• 91762 [C] - 1 violation
• 91764 [C]
• 91798

Data Sources

• Water quality: EPA Safe Drinking Water Information System (SDWIS)
• Lead/copper: EPA Lead and Copper Rule sampling data
• Radon: EPA Map of Radon Zones

Reporting periods vary by source. Missing data is shown as unavailable, not as zero.

Housing Age Profile

Ontario's housing stock is predominantly older, with a median build year of 1979 that reflects decades of construction before federal plumbing standards were tightened. The 1986 ban on lead solder and the pre-1970 era of lead service lines are both relevant benchmarks here - a significant share of the residential inventory predates one or both of those cutoffs, creating an elevated baseline for plumbing-related lead risk that aggregate water quality data may not fully reflect at the household level.

1979

Median Year Built

65%

Pre-1986 (Lead Paint Risk)

24%

Pre-1970 (Lead Pipes Risk)

Pre-1970 (24%) 1970–1986 (41%) Post-1986 (35%)

Over half of homes in Ontario were built before 1986, when lead solder was banned. Older plumbing may leach lead into drinking water, especially with corrosive water chemistry.

Source: U.S. Census Bureau ACS B25034.

Ontario: Remediation Cost in Perspective

Placing remediation in the context of Ontario's property market, the equity share is low - most homeowners here are weighing a financial commitment that fits comfortably within routine property planning, far from the threshold where remediation becomes a material equity decision rather than a standard upkeep consideration.

Median Home Value

$568,700

Est. Remediation

$1,480

Remediation as % of home value 0.3%

Remediation costs in Ontario are relatively low compared to home values. The $720–$2,360 estimated range is a small fraction of median property value. Home values are 23% below the California average.

Protecting Children from Lead in Ontario

65%

Homes Built Before 1986

0.0007

mg/L Avg Lead (Limit: 0.015)

Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.

Before the federal solder ban, lead solder was a routine plumbing material, and 65% of the Ontario inventory was built in that earlier era - a share large enough to move household-level reads onto the standard list.

Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.

Historical Flood-Claim Evidence for Ontario

21

Total FEMA Flood Claims

$3,137

Avg Reported Sum With Payment Data

50%

A/V Share of Claim-Record ZIPs

Historical NFIP data for Ontario contains 21 flood insurance claims. Among claims with payment data, the average reported building, contents, and ICC component sum is $3,137. Among ZIP codes with claim records, 50% have an A- or V-family dominant rated zone recorded in those historical claims. This is not a complete current FEMA property-map inventory.

How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. The <strong>$1,480</strong> remediation estimate shown here excludes flood insurance and is not derived from NFIP claim count.

Claim count does not establish current property risk. Check the exact address in FEMA's current map and obtain a property-specific insurance quote when relevant.

Source: historical FEMA National Flood Insurance Program (NFIP) claim records. No current FEMA property-map designation is asserted.