Water Quality in Cos Cob, CT: No Violations — Grade D
Grade D · Score 40/100 · 1 water system · Updated 2026-05-03
Cos Cob's water has significant violations. Water testing and filtration are recommended.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
Federal compliance data for Cos Cob, CT: no violations across 1 monitored system.
Water Quality by ZIP Code in Cos Cob
Water quality varies across Cos Cob's 1 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 06807 | D | 40 | 0 | 0 | View report → |
Water Quality Overview
Cos Cob, Connecticut receives a water quality grade of D with an overall score of 40 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 1 water system serving Cos Cob. This is a positive indicator, though it does not guarantee the absence of all contaminants — some substances (like PFAS) are not yet fully regulated.
What Grade D Means
A grade of D indicates significant compliance issues. Cos Cob's water systems have accumulated violations that suggest ongoing water quality challenges. Residents should check their specific ZIP code report and consider water testing or filtration.
Lead Levels
Lead testing data for Cos Cob is currently being collected. The EPA requires all community water systems to test for lead under the Lead and Copper Rule.
With 77% of homes built before 1986, Cos Cob has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Radon Risk
Cos Cob is in EPA Radon Zone 1 (High risk). The EPA recommends all homes in Zone 1 areas be tested for radon. Radon is the second leading cause of lung cancer after smoking.
Water Systems Serving Cos Cob
Cos Cob is served by 1 community water system regulated under the Safe Drinking Water Act. These systems collectively serve approximately 567 people across 1 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
How to Check Your Water in Cos Cob
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
Cos Cob vs. Nearby Connecticut Cities
How Cos Cob's water quality compares to similar cities in Connecticut:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Cos Cob | D | 0 | 1 | 567 |
| Greenwich | C | 0 | 1 | 567 |
| Prospect | C | 7 | 2 | 567 |
| Mashantucket | C | 7 | 1 | 550 |
Common Questions About Cos Cob Water
These are the most common questions residents search for about water quality in Cos Cob, Connecticut:
Is Cos Cob water hard or soft? Water hardness varies by source. Cos Cob's 1 water system uses a single source. Check your ZIP code report for specific hardness data.
Can I drink Cos Cob tap water? Cos Cob's water receives a grade of D (40/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Cos Cob? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Cos Cob vs. Connecticut Average
Understanding how Cos Cob compares to the broader Connecticut average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Cos Cob.
ZIP Codes in Cos Cob
Cos Cob spans 1 ZIP code. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
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
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.