Within Mount Hamilton, safety indicators for tap water remain above the CA median — documented violations are infrequent and the city's compliance record sits in the upper tier.

Data: EPA SDWIS Last verified: 2026-06-03

Overview

We track water quality and home safety data for 1 ZIP code in Mount Hamilton, California (population ~41), covering 2 community water systems serving approximately 1,040,204 people region-wide.

No EPA violations recorded across any ZIP codes in Mount Hamilton — an excellent indicator of water quality.

Home Safety Score

Average Home Safety Score for Mount Hamilton: B (83/100)

The score combines three factors:

Factor	What It Measures
Water Quality	EPA violations and compliance history
Lead Levels	90th percentile lead concentration vs EPA action level
Radon Risk	EPA radon zone classification

Water Sources

Mount Hamilton water systems draw from: Surface water.

Lead & Copper

• Average lead level (90th percentile): 0.0032 mg/L (EPA action level: 0.015 mg/L)
• 0 ZIP codes exceed the EPA lead action level

Radon Risk

Dominant radon zone: Zone 2 (Moderate Risk)

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

Areas with No Violations

All ZIP Codes in Mount Hamilton

• 95140 [B]

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

Updated daily.

Housing Age Profile

Pre-1986 plumbing is not a rare legacy case in Mount Hamilton — it's the dominant profile. The median build year of 1987 indicates a housing stock where lead-soldered copper joints are a common structural feature of residences across the city.

1987

Median Year Built

68%

Pre-1986 (Lead Paint Risk)

42%

Pre-1970 (Lead Pipes Risk)

Pre-1970 (42%) 1970–1986 (26%) Post-1986 (32%)

Over half of homes in Mount Hamilton 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.

How Remediation Costs Compare in Mount Hamilton

Equity impact data for Mount Hamilton lands in the favorable tier — remediation claims a small slice of what properties here are worth.

Median Home Value

$2.0M

Est. Remediation

$400

Remediation as % of home value 0.0%

Remediation costs in Mount Hamilton are relatively low compared to home values. The $0–$800 estimated range is a small fraction of median property value. Home values are 171% above the California average.

Mount Hamilton: Lead Risk & Vulnerable Populations

68%

Homes Built Before 1986

0.0032

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.

Despite citywide averages serving as the standard public reference point, those aggregates cannot resolve what is happening at one specific faucet — and where 68% of Mount Hamilton homes come from before the solder rule or where utility samples sit at or above the action mark, the gap between system data and faucet reality matters more than it does in lower-exposure communities. An in-home draw closes that gap, with certified filtration through retailer networks available where confirmed faucet results warrant additional measures.

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