How to read your water-quality report

Consumer Confidence Reports can tell you where your drinking water comes from, which regulated contaminants were detected, and whether the system met applicable standards. The key is knowing what the numbers mean—and what the report does not tell you.

Last reviewed: October 2026

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15-second takeaway A water-quality report is best read as a summary of a public water system’s monitoring and compliance, not as a laboratory report for your individual faucet. Start with the source, then the contaminant table, then look for violations, health information, and notes about where and when samples were collected.

What kind of report is this?

For most people served by a community water system, the annual drinking-water report is called a Consumer Confidence Report, or CCR. EPA requires community water systems to provide these reports to customers. As of 2026, reports are generally delivered each year by July 1 and summarize information about the previous year’s water quality. (U.S. Environmental Protection Agency [EPA], 2025a)

A CCR typically includes the source of the drinking water, detected regulated contaminants, applicable drinking-water standards, information about violations, and contact information for the water system. Some reports also include source-water assessments, treatment information, or additional monitoring results. (EPA, 2025a)

Private wells are different. Individual well owners generally do not receive a CCR because private household wells are not regulated as community water systems under the federal Safe Drinking Water Act. Private well owners are responsible for ensuring the safety of their household drinking water. (EPA, 2026)

Start with the source of your water

Before reading the contaminant table, find the section that identifies where the water comes from.

A system may rely on a river, reservoir, lake, aquifer, wells, or a combination of sources. The report may also summarize potential sources of contamination in the surrounding watershed or source-water area. EPA requires CCRs to identify the drinking-water source and provide information about source-water vulnerability where available. (EPA, 2025a)

This context matters because source water influences what treatment is needed and which contaminants may reasonably be monitored or discussed.

Find the contaminant table

The most technical part of a CCR is usually a table listing contaminants detected during required monitoring.

The table generally includes the contaminant name, the level detected, the applicable regulatory limit or treatment requirement, the range of results where relevant, whether a violation occurred, and a typical source of the contaminant. EPA requires detected contaminants subject to mandatory monitoring to be reported in the CCR in standardized ways.

A useful first question is therefore not simply, “Was something detected?” but:

How does the detected level compare with the applicable standard?

Detection by itself does not necessarily mean the water presents a health risk. Many substances can be measured at concentrations well below regulatory limits.

MCL and MCLG: two numbers with different meanings

Two abbreviations appear frequently in drinking-water reports.

MCL — Maximum Contaminant Level
The MCL is the highest level of a contaminant allowed in drinking water under the federal drinking-water regulations. It is enforceable.

MCLG — Maximum Contaminant Level Goal
The MCLG is a non-enforceable public-health goal: the level below which there is no known or expected health risk, allowing a margin of safety.

EPA sets MCLs as close to MCLGs as feasible, taking treatment technology and other regulatory considerations into account.

This means an MCL and an MCLG do not serve the same purpose. A result above an MCLG but below the MCL is not automatically a regulatory violation.

Action levels and treatment techniques

Not every drinking-water rule uses an MCL.

Some contaminants are regulated through an Action Level (AL). An action level is a concentration that, when exceeded under the rule’s specified monitoring framework, triggers treatment or other requirements for the water system.

Other contaminants are regulated through a Treatment Technique (TT)—a required treatment process or procedure intended to reduce contamination rather than a single numerical maximum concentration.

Lead is a useful example of why these distinctions matter. Its regulatory framework does not work like a conventional household pass/fail MCL. For more detail, see Lead in Drinking Water.

Read the units carefully

Concentrations in CCRs are often reported in:

• ppm — parts per million, approximately equivalent to milligrams per liter for water
• ppb — parts per billion, approximately equivalent to micrograms per liter
• ppt — parts per trillion, used for some contaminants at very low concentrations
• pCi/L — picocuries per liter, used for radioactivity

A ppb value is one-thousandth of a ppm value. That means the units must be the same before two numbers are compared.

EPA requires contaminant levels and corresponding standards in the CCR table to be presented in comparable units. (EPA, 2010)

“Detected” does not mean “unsafe”

A contaminant can appear in a CCR because it was detected, even when the concentration is well below the regulatory limit.

Likewise, ND, or “not detected,” does not mean that absolutely none of the substance exists. It generally means that the substance was not detected at or above the analytical method’s reporting or detection threshold. (EPA, 2010)

So three different statements should not be treated as equivalent:

Detected
A measurable amount was found.

Above the MCL or other applicable regulatory threshold
The result may constitute or contribute to a regulatory exceedance, depending on the rule.

Not detected
The laboratory did not detect the contaminant at or above the applicable analytical threshold.

Those distinctions prevent both unnecessary alarm and false reassurance.

Why some results may be older than one year

A CCR usually summarizes the previous calendar year, but not every contaminant is necessarily tested every year.

Some contaminants are monitored less frequently because their concentrations are not expected to change rapidly or because the applicable rule permits reduced monitoring. In those cases, the CCR may report the most recent representative result and the year in which the sample was collected. EPA allows older monitoring data to appear when monitoring is required less frequently and requires the report to indicate that the data came from earlier testing. (EPA, 2010)

An older sample date is therefore not automatically evidence that the utility failed to test when required.

Look for violations and health information

A CCR should make regulatory violations identifiable.

If the system violated a drinking-water requirement, the report should explain the violation and may include information about potential health effects and what the system is doing to correct the problem. EPA’s CCR requirements specifically include reporting on compliance with drinking-water regulations and, where applicable, health-effects information.

This is the part of a report that deserves particularly careful reading. A detected contaminant below its applicable limit is a different situation from a reported violation.

The report describes a water system, not necessarily your faucet

A CCR summarizes monitoring conducted for the public water system. It is not normally a laboratory analysis of the water coming from your particular kitchen tap.

Water may change after leaving the treatment plant as it travels through mains, storage facilities, service lines, and building plumbing. Lead and copper are especially important examples because plumbing materials can affect water after treatment.

That is why a utility report and a household tap test can answer different questions.

A CCR may tell you a great deal about the system serving your home. It usually cannot tell you with certainty what is happening inside your own service line or household plumbing.

What if a number concerns you?

First, identify what the number represents:

• Is it a detected concentration, an average, a range, a 90th percentile, or another regulatory statistic?
• What unit is being used?
• What standard or goal is shown beside it?
• Was there a violation?
• When and where was the sample collected?
• Does the contaminant originate mainly in source water, treatment, the distribution system, or household plumbing?

Then read the explanatory notes associated with the table before drawing conclusions.

If something remains unclear, the water system contact listed in the CCR is the logical first source for clarification. State drinking-water programs can also provide regulatory context.

Changes beginning in 2027

The federal CCR requirements are changing.

EPA finalized revisions to the Consumer Confidence Report Rule in 2024. Beginning in 2027, the revisions are intended to make reports clearer and more accessible, expand information related to lead, improve language access, and allow broader use of electronic delivery. Systems serving 10,000 or more people will be required to provide CCRs twice per year rather than only annually. (EPA, 2024)

The first report will continue to provide the annual summary. When applicable, the second report must also include a six-month update for systems that had violations, action-level exceedances, or received results under the Unregulated Contaminant Monitoring Rule.

For readers in 2026, the practical point is simply that the format and frequency of some CCRs will change beginning next year.

How H2O IQ fits in

A Consumer Confidence Report is one source of drinking-water information.

H2O IQ’s Explore Your Water tool provides access to public monitoring data from other sources as well. Those records can help investigate local conditions, but they should not automatically be treated as substitutes for a utility’s CCR—or as direct measurements of a particular household faucet.

Different datasets answer different questions.

The CCR is especially useful for understanding your public water system’s regulated drinking-water monitoring and compliance.

The larger picture

A water-quality report becomes much easier to read once the reader stops treating it as a simple “safe/unsafe” certificate.

It is a structured summary of a monitoring system.

The useful questions are:

What was tested? What was found? How does the result compare with the applicable standard? Was there a violation? Where and when was the sample collected? And does the result describe the whole system—or something closer to my own tap?

Those questions turn a dense regulatory table into information that can actually support proportionate decisions.