Greenwich, CT: High Radon Risk — 59/100 (2026)
3 ZIP codes · 2 water systems · Updated 2026-06-03
Water monitoring across Greenwich paints a mid-range picture within CT — solid compliance in some service zones, documented concerns in others. Most violations on record are concentrated in specific areas, and the overall grade has held in the middle tier without major shifts in recent monitoring cycles.
How Greenwich Compares
Data: EPA SDWIS Last verified: 2026-06-03
Greenwich Water: The Quick Version
- Average lead level: 0.0012 mg/L.
- Homes built before 1986: 75% — older plumbing may contain lead solder.
- Estimated remediation: $2,800 per household.
Water Systems Serving Greenwich
Across Greenwich, CT, residential water comes from 2 primary utilities rather than a single consolidated provider. Each system operates independently — managing its own distribution infrastructure, rate schedules, and EPA compliance filings. Federal records track 2 water systems in the area, with these top providers accounting for the majority of residential connections.
Overview
We track water quality and home safety data for 3 ZIP codes in Greenwich, Connecticut (population ~39,575), covering 2 community water systems serving approximately 352,323 people region-wide.
No EPA violations recorded across any ZIP codes in Greenwich — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Greenwich: C (59/100)
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
Greenwich water systems draw from: Groundwater.
Lead & Copper
- Average lead level (90th percentile): 0.0012 mg/L (EPA action level: 0.015 mg/L)
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 1 (High Risk)
- Zone 1 (High): 3 ZIP codes
- Zone 2 (Moderate): 0 ZIP codes
- Zone 3 (Low): 0 ZIP codes
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 06830 | C | AQUARION-EASTERN FAIRFIELD COUNTY | 351,756 |
| 06831 | C | AQUARION-EASTERN FAIRFIELD COUNTY | 351,756 |
| 06836 | C | Brunswick School (lower & Lower Middle) | 567 |
All ZIP Codes in Greenwich
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.
How Old Is Greenwich's Housing Stock?
With 75% 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
The character of Greenwich's housing stock is one of deep historical layering — a median build year of 1965 signals a city built largely before the plumbing era changes of 1986 and 1970. Lead-soldered copper joints and, in the oldest properties, lead service lines are commonly present in this inventory. That context shapes what individual water testing may reveal, particularly in neighborhoods where the oldest housing is concentrated.
Over half of homes in Greenwich 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.
Greenwich: Remediation Cost in Perspective
At current valuations, Greenwich sits in the low remediation-share tier — the equity impact of fixing documented issues is proportionally minor.
Remediation costs in Greenwich are relatively low compared to home values. The $1,867–$3,700 estimated range is a small fraction of median property value. Home values are 313% above the Connecticut average.
Protecting Children from Lead in Greenwich
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.
75% — that captures the slice of Greenwich housing dating from before the federal ban on solder containing lead. It pairs with aggregate utility readings that either approach or cross 0.015 mg/L, the benchmark set under the EPA Lead and Copper Rule. Together, the two figures shift one-home reads into a standard household-level confirmation, particularly for families with kids. A certified lead-removal filter is available through retailer-verified channels if a kit returns results that warrant additional measures.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Climate-Related Water Risk for Greenwich
The National Flood Insurance Program builds its dataset one claim at a time — each filed claim represents a property where flood damage was severe enough to trigger an insurance payout. For Greenwich, that dataset has accumulated 526 such events across the program's multi-decade history. 67% of ZIP codes here carry official FEMA flood zone designations, reflecting federal assessments of where flood risk is concentrated. Together, those data points describe a community with a documented, substantial flood exposure — the kind that shapes not just property risk but also the periodic reliability of water supply infrastructure. When flood events reach that scale, treatment systems face peak-load contamination stress, private wells become vulnerable to surface water intrusion, and the distribution network can experience backflow conditions that allow untreated water to re-enter the system.
Greenwich has a significant flood history with 526 FEMA flood insurance claims on record, averaging $27,433 per claim. With 67% of ZIP codes in FEMA-designated flood zones, flood risk is a major concern for homeowners and water quality.
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>$2,800</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.
What You Can Do in Greenwich
- Test your water at home. City-level data shows averages — your tap may differ. NSF-certified test kits cost $20-40 and give results in days.
- Install a certified water filter. An NSF-certified pitcher or under-sink filter removes most common contaminants.
- Check your home's plumbing. With 75% of homes built before 1986, lead solder is a real possibility.
Deep Dive Reports
Detailed analysis for Greenwich, CT