Water Quality in Darien, CT: No Violations - Grade F
Grade F · Score 35/100 · 3 water systems · Updated 2026-07-18
Darien's water has serious compliance issues. Independent testing and filtration are strongly recommended.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-07-18
Utilities in Darien, CT have maintained an unbroken clean record - the EPA compliance database documents no health-based exceedances, no reportable monitoring failures, and no enforcement proceedings across all 3 tracked public water systems.
Water Quality by ZIP Code in Darien
Darien is covered by a single ZIP code, so one water-quality profile applies citywide. See the contaminant data below.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 06820 | F | 35 | 0 | 0 | View report → |
Water Quality Overview
Darien, Connecticut receives a water quality grade of F with an overall score of 35 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 3 water systems serving Darien. 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 F Means
A grade of F indicates serious compliance issues. Darien's water systems have substantial violations. Residents should strongly consider independent water testing and appropriate filtration.
Lead Levels
Lead testing data for Darien is currently being collected. The EPA requires all community water systems to test for lead under the Lead and Copper Rule.
With 74% of homes built before 1986, Darien 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
Darien 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 Darien
Darien is served by 3 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 21,683 people across 1 ZIP code.
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
The EPA has taken 10 enforcement actions against water systems serving Darien. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Darien
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
EPA Enforcement History
The EPA and state regulators have taken 10 enforcement actions against water systems serving Darien. Recent actions:
| Date | Action Type |
|---|---|
| 2025-05-21 | State Order Extension |
| 2025-05-21 | State Informal Action |
| 2025-04-10 | State Informal Action |
| 2025-03-10 | State Informal Action |
| 2025-03-10 | State Informal Enforcement |
| 2024-12-31 | State Order Extension |
| 2024-08-28 | State Informal Action |
| 2024-08-01 | State Informal Action |
| 2024-07-10 | State Order Extension |
| 2024-06-06 | State Informal Action |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2025-05-21.
Darien vs. Nearby Connecticut Cities
How Darien's water quality compares to similar cities in Connecticut:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Darien | F | 0 | 3 | 21,683 |
| Bloomfield | C | 30 | 5 | 21,547 |
| Guilford | C | 1 | 3 | 22,037 |
| Rocky Hill | B | 6 | 3 | 20,716 |
Common Questions About Darien Water
These are the most common questions residents search for about water quality in Darien, Connecticut:
Is Darien water hard or soft? Water hardness varies by source. Darien's 3 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Darien tap water? Darien's water receives a grade of F (35/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Darien? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Darien vs. Connecticut Average
Understanding how Darien 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 Darien.
ZIP Codes in Darien
Darien 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.