San Dimas, CA Water Safety: 83/100 (2026)
1 ZIP code · 9 water systems · Updated 2026-06-03
Water utilities in San Dimas have maintained a consistent compliance record over recent monitoring periods — the city's above-average grade in CA reflects low violation rates and no systemic health concerns flagged in current data.
How San Dimas Compares
Data: EPA SDWIS Last verified: 2026-06-03
San Dimas Water: The Quick Version
- Average lead level: 0.0032 mg/L.
- Homes built before 1986: 77% — older plumbing may contain lead solder.
- Estimated remediation: $1,800 per household.
- CDC health risk index: 10.71.
Water Systems Serving San Dimas
9 water systems are tracked federally in San Dimas, CA. The top 3 providers collectively serve most residential addresses, but because they operate independently, infrastructure maintenance standards and compliance histories differ from one service zone to another.
Overview
We track water quality and home safety data for 1 ZIP code in San Dimas, California (population ~33,917), covering 9 community water systems serving approximately 240,177 people region-wide.
No EPA violations recorded across any ZIP codes in San Dimas — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for San Dimas: 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
San Dimas water systems draw from: Groundwater, 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
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 91773 | B | Gswc-san Dimas | 56,538 |
All ZIP Codes in San Dimas
- 91773 [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.
CDC Health Data for San Dimas
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
How Old Is San Dimas's Housing Stock?
With 77% of homes built before 1986, lead solder in plumbing is a potential concern. The EPA banned lead solder in 1986, but many older homes retain original plumbing.
Source: U.S. Census Bureau American Community Survey (ACS).
Housing Age Profile
Reading the housing age data for San Dimas — median build year 1974 — the overriding implication is that the plumbing materials inside a typical home here reflect pre-1986 construction standards. In practical terms, that means lead-soldered copper joints are common across much of the housing stock. Where those materials are present, water can leach lead as it moves through joints — a pathway that corrosion control treatment under federal rules is designed to reduce, though it cannot eliminate lead risk where the plumbing materials themselves contain lead.
Over half of homes in San Dimas 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.
San Dimas: Remediation Cost in Perspective
Property equity in San Dimas runs well ahead of estimated remediation costs — a cost-to-value ratio that sits in the low tier, meaning documented water and safety issues here are the kind homeowners can plan to address without treating the expense as a significant budget event relative to what their homes are worth.
Remediation costs in San Dimas are relatively low compared to home values. The $1,200–$2,600 estimated range is a small fraction of median property value. Home values are 2% above the California average.
Protecting Children from Lead in San Dimas
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.
Pulling a tap sample fills the gap that utility data cannot close, particularly here where 77% of housing dates from the pre-rule era and citywide monitoring sits at or above the regulatory mark in San Dimas.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Climate-Related Water Risk for San Dimas
Multiple flood events have been recorded for San Dimas through the NFIP — 8 claims in total, with 100% of ZIP codes in FEMA-designated zones — pointing to a flood exposure profile that merits inclusion in a water quality assessment without reaching high-severity planning territory.
San Dimas has a moderate flood history with 8 FEMA claims averaging $641 per payout. 100% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
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. Flood damage can add significantly to the estimated <strong>$1,800</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
Deep Dive Reports
Detailed analysis for San Dimas, CA