Every year, by July 1, every Connecticut water utility mails or posts online a Consumer Confidence Report — a document that tells you what was found in your water during the previous year and how it compares to federal and state standards.
Most people throw it away. The ones who read it often come away either falsely reassured or unnecessarily alarmed, because the report is written in regulatory language that requires translation.
Here's the translation.
What the Report Actually Contains
The CCR lists detected contaminants — chemicals, metals, and microorganisms that were found in the water system during testing — along with:
- The highest level detected (or the range of detected levels)
- The EPA's Maximum Contaminant Level (MCL) — the legal limit
- The MCL Goal (MCLG) — the level at which no known health risk exists (often zero for carcinogens)
- The likely source of the contaminant
The report covers contaminants that the EPA requires utilities to test for. It does not cover contaminants that the EPA doesn't require testing for — and there are many.
What Does "ND" Mean on Your Water Report?
"ND" in a CCR means "not detected." It does not mean "not present."
Every test has a detection limit — a minimum concentration below which the test cannot reliably identify the contaminant. If a contaminant is present at a level below the detection limit, the test returns "ND." The contaminant may still be there.
This matters most for PFAS. The EPA's new PFAS limits are set at 4-10 parts per trillion — extraordinarily low concentrations. Many older PFAS tests had detection limits higher than the new MCLs. A CCR from 2022 that says "PFAS: ND" may have been using a test that couldn't detect PFAS at the levels that are now considered unsafe. If you live in Fairfield County, this is especially relevant — Aquarion's PFAS compliance deadline isn't until 2031.
The MCL vs. MCLG Gap
For many contaminants, the MCL (the legal limit) and the MCLG (the health-based goal) are different numbers. Sometimes very different.
For lead, the MCLG is zero. There is no safe level of lead in drinking water. The MCL — the legal limit that triggers regulatory action — is 15 parts per billion (as a 90th percentile of samples). A system can have lead levels up to 14.9 ppb in 90% of its samples and be in full compliance with the law, while the health-based goal is zero.
For trihalomethanes (disinfection byproducts), the MCLG for chloroform is zero (it's a probable carcinogen). The MCL is 80 ppb. A CCR that says your THM level is 60 ppb and "meets MCL" is telling you the legal limit is satisfied. It is not telling you the health-based goal is met.
When you read a CCR, look at the MCLG column, not just the MCL column. The MCLG tells you what the EPA considers truly safe. The MCL tells you what's legally required.
What the Report Doesn't Tell You
Your household level. The CCR reports system averages and the highest detected level across the system. Your tap may be higher or lower than the system average, depending on your home's plumbing, your proximity to the water main, and your service line material.
Private well data. If you're on a private well, there is no CCR for your water. You are responsible for your own testing.
Unregulated contaminants. PFAS was not regulated until 2024. Before that, it didn't appear in CCRs even if it was present. There are other contaminants — some emerging, some simply not yet regulated — that may be in your water and won't appear in any CCR.
What happened last week. The CCR covers the previous calendar year. A contamination event that happened after the reporting period won't appear until next year's report.
How to Use the Report Effectively
Read the MCLG column, not just the MCL column. If the MCLG is zero and the detected level is above zero, you have a contaminant present that the EPA considers to have no safe level.
Look for footnotes. CCRs often include footnotes explaining why certain results are listed as "meets MCL" despite being above zero. These footnotes sometimes contain important context.
Use the report as a starting point, not an endpoint. The CCR tells you what the utility found in its system-wide testing. It doesn't tell you what's coming out of your specific tap. If the CCR shows any detected lead, any detected PFAS, or any detected disinfection byproducts, consider household-level testing or filtration. For a town-by-town breakdown of what to look for, see our Connecticut water quality guide.
Ready to check your own water? Enter your ZIP code at CheckYourTap.com to see what's in your tap water — free, in 30 seconds.
And if you're on a private well — the CCR is irrelevant to you. Test your own water.
Keep Reading
- A Practical Guide to Water Quality in Connecticut's Major Towns — What's Actually in the Water Where You Live
- Boiling Your Water Removes Some Things and Concentrates Others. Know the Difference Before You Boil.
- The Water Test Your Bank Required Doesn't Test for What's Actually Dangerous
Frequently Asked Questions
What is the difference between MCL and MCLG in a water report?
The MCL (Maximum Contaminant Level) is the legal limit — the highest level allowed by law. The MCLG (Maximum Contaminant Level Goal) is the health-based target where no known health risk exists. For lead, the MCL is 15 ppb but the MCLG is zero. Always check the MCLG column to understand actual health risk.
Does "ND" on a water report mean my water is clean?
No. "ND" means "not detected" — the contaminant wasn't found above the test's detection limit. It may still be present at lower concentrations. This is especially important for PFAS, where the EPA's new limits (4-10 parts per trillion) are below what many older tests could detect.
Does my water quality report show what's actually in my tap?
Not exactly. The CCR reports system-wide averages and the highest detected levels across the utility. Your individual tap may be higher or lower depending on your home's plumbing, service line material, and proximity to the water main. If you're on a private well, there is no CCR for your water at all.
Sources: EPA Consumer Confidence Report Rule; CT DPH CCR Guidance; EPA Drinking Water Standards and Health Advisories; NSF International Water Testing Guide; checkyourtap.com Water Quality Data.