How to Read a Water Quality Report
A Consumer Confidence Report covers a lot of technical ground. Here's a section-by-section walkthrough so the numbers and abbreviations actually mean something.
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Who this page is for
Anyone staring at a CCR wondering what it actually says
Consumer Confidence Reports follow a standard federal format, which is good news once you know what to look for — every report you'll ever open has roughly the same sections in roughly the same order. This guide walks through each one, in the order they typically appear, along with the abbreviations that trip most people up on a first read.
Section 1
Source water information
Every CCR opens by identifying where the water comes from — typically a surface water source (a river or reservoir), a groundwater source (wells drawing from an aquifer), or a mix of both. Many systems also reference a source water assessment, a one-time study of potential contamination risks near the water source, which is different from ongoing water quality monitoring.
Section 2
The detected contaminants table
This is the core of the report, and the part most people skim past because of the abbreviations. The table typically has columns for the substance name, the level detected (often as a range and an average), the MCL or action level it's compared against, the MCLG, and the likely source of the substance (for example, "erosion of natural deposits" or "runoff from fertilizer use"). Here's what the key abbreviations mean:
- MCL (Maximum Contaminant Level): The legal limit for a substance in drinking water — the enforceable standard
- MCLG (Maximum Contaminant Level Goal): The level below which there is no known or expected health risk, which is sometimes set at zero for substances with no safe threshold
- AL (Action Level): Used specifically for lead and copper — the concentration that triggers required treatment or other action if exceeded
- TT (Treatment Technique): A required process rather than a numeric limit, used when it's not feasible to measure a contaminant directly
- ppb / ppm: Parts per billion and parts per million — the units most results are reported in. One ppb is roughly equivalent to one drop in an Olympic swimming pool
- ND: Not detected — the substance was tested for and not found above the lab's detection threshold
Section 3
Violations and compliance status
If a system had any violations during the reporting year, the CCR is required to describe them, along with what the system did in response and what customers should do, if anything. It's worth distinguishing two categories: monitoring or reporting violations (a missed sampling deadline or paperwork issue, with no indication water quality was actually compromised) and health-based violations (an actual exceedance of an MCL or treatment technique requirement). The report should specify which type occurred.
Section 4
Required health-effects language
Federal rules require every CCR to include certain standardized language about vulnerable populations (such as those with compromised immune systems) and general information about contaminants that can be found in drinking water. This boilerplate language appears on every CCR nationwide by law — its presence isn't a signal that your specific water has a problem, it's a required disclosure regardless of your system's actual results.
Putting it together
What's normal vs. what's worth a follow-up call
Most CCRs show a handful of substances detected at low levels, well under their MCLs, with sources like natural mineral erosion or standard water treatment byproducts. That's expected and not a cause for concern. What's worth a closer look:
- Any detected level at or above its MCL or action level
- A listed violation, especially a health-based one
- A result trending upward year over year even if still under the MCL
- Any substance you don't recognize and want to understand better before deciding on treatment
Common mistakes
Mistakes to avoid
- Treating any detection at all as alarming, rather than comparing it to the MCL
- Confusing the MCL (legal limit) with the MCLG (health-based goal), which are often different numbers for the same substance
- Skipping the violations section because the contaminant table looked fine
- Assuming required health-effects boilerplate language is specific to your water rather than standardized federal disclosure text
When to get help
When to get professional help
If your report shows a violation you don't understand, a result trending toward its MCL, or you simply want a professional opinion on what your specific results mean for your household, a local water treatment provider can help interpret the report and recommend appropriate next steps.
Official sources
Official source links
FAQ
Frequently asked questions
What does "ND" mean on my water report?
ND means "not detected." It indicates the substance was tested for and found at a level below the laboratory's detection limit — effectively, it wasn't found in a measurable amount.
Is any detected contaminant a problem?
Not necessarily. Reports list detections down to very small trace amounts, well below levels of concern, alongside the maximum contaminant level (MCL) they're compared against. The relevant question is how a detected level compares to its MCL and MCLG, not whether it was detected at all.
What's the difference between MCL and MCLG?
The Maximum Contaminant Level (MCL) is the enforceable legal limit. The Maximum Contaminant Level Goal (MCLG) is the level below which there is no known or expected health risk, which may be set lower than the MCL to account for treatment feasibility and cost. Water systems are required to stay at or below the MCL.
My report mentions a violation. Should I be worried?
Read the specific violation type and the system's response, which the report is required to include. Monitoring and reporting violations (a missed test or paperwork deadline) are different from a health-based violation (an actual exceedance of a safety standard) — the report should specify which occurred and what corrective action was taken.
NY Water Quality Guide is an independent educational resource and is not affiliated with or endorsed by the New York State Department of Health, the EPA, or any water utility. This page explains how to read standard CCR terminology and is not a substitute for consulting your provider or a water treatment professional about your specific report.
Last reviewed: July 9, 2026
Worksheet
Download the CCR Reading Worksheet
Fill in your system details and log any contaminant you want to understand or ask your utility about while you read your Consumer Confidence Report. It is a free, printable, fillable PDF — print it or fill it in and save it as a PDF.