Cos Cob, CT: High Radon Risk — 40/100 (2026)
1 ZIP code · 2 water systems · Updated 2026-06-03
Cos Cob ranks below average for tap water safety in CT — health-based violations are documented across multiple service areas in recent EPA monitoring data.
How Cos Cob Compares
Data: EPA SDWIS Last verified: 2026-06-03
What You Should Know About Cos Cob Water
- Homes built before 1986: 77% — older plumbing may contain lead solder.
- Estimated remediation: $3,000 per household.
Who Supplies Your Water in Cos Cob
Federal drinking water records identify 2 systems in Cos Cob, CT. The leading 2 providers serve the largest share of residential connections, each operating as a separate entity with its own rate authority, infrastructure management, and EPA compliance obligations — so service conditions are not uniform city-wide.
Overview
We track water quality and home safety data for 1 ZIP code in Cos Cob, Connecticut (population ~7,667), covering 2 community water systems serving approximately 352,323 people region-wide.
No EPA violations recorded across any ZIP codes in Cos Cob — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Cos Cob: D (40/100)
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
Cos Cob water systems draw from: Groundwater.
Lead & Copper
- Lead data: not yet available for Cos Cob
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 1 (High 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 |
|---|---|---|---|
| 06807 | D | AQUARION-EASTERN FAIRFIELD COUNTY | 351,756 |
All ZIP Codes in Cos Cob
- 06807 [D]
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 & Infrastructure in Cos Cob
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
Cos Cob's housing stock is predominantly older, with a median build year of 1966 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.
Over half of homes in Cos Cob 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.
Cost Context: What Remediation Means for Cos Cob Homeowners
Setting Cos Cob remediation figures against its property market, the resulting ratio sits comfortably in the low tier — a classification that reflects the kind of household financial position where most homeowners can identify documented issues, schedule the work, and absorb the cost without it registering as a significant budget disruption.
Remediation costs in Cos Cob are relatively low compared to home values. The $2,000–$4,100 estimated range is a small fraction of median property value. Home values are 201% above the Connecticut average.
Lead Exposure Risk for Children in Cos Cob
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.
77% of Cos Cob housing dates to the pre-rule era, alongside aggregate readings hovering at the federal action mark — household-level confirmation through a draw-test kit fits the local picture.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Flood & Climate Risk in Cos Cob
Flood activity in Cos Cob is neither negligible nor at the level of the highest-exposure areas in the NFIP dataset. The 124-claim record and 100% flood zone coverage suggest a community that has experienced recurrent events but has not faced the kind of sustained, severe exposure where water-supply contamination becomes a primary public health concern. It sits in a middle range where flood history merits inclusion in any complete local water quality picture.
Cos Cob has a moderate flood history with 124 FEMA claims averaging $17,265 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>$3,000</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 Cos Cob
- 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 77% of homes built before 1986, lead solder is a real possibility.
- Review your water system's CCR. Your utility publishes an annual Consumer Confidence Report with detailed test results. Request it or find it online.
Deep Dive Reports
Detailed analysis for Cos Cob, CT