What is the difference between MCL and MCLG?

The MCLG (goal) is the level at which no known or expected health risk exists, set without regard to cost or feasibility. The MCL (limit) is the enforceable standard, set as close to the goal as technology and cost allow. When the two differ widely — as with arsenic (goal 0, limit 10 ppb) — it reflects a trade-off, not a safety guarantee.

My report lists a violation. Should I stop drinking the water?

Read the type. Monitoring and reporting violations are paperwork failures that usually pose no direct risk. Health-based (MCL or treatment technique) violations are more serious; the report must explain the potential health effects and what the utility did. If a violation involved bacteria, nitrate or a boil-water notice, the utility should have notified you at the time.

Why does the report show a range instead of one number?

Utilities sample at multiple locations and times. The range shows the lowest and highest individual results; the "level detected" is typically the highest value or the running annual average used for compliance. A wide range usually reflects seasonal changes or differences between parts of the distribution system.

How do I get a CCR for a home I am thinking of buying?

Search the local utility's website — reports are public — or request it from the utility directly. For homes on private wells, ask the seller for recent laboratory results and arrange your own certified test as part of the inspection.

City Water

How to Read Your Utility’s Consumer Confidence Report (CCR) Without a Chemistry Degree

Every July your water utility publishes a report full of acronyms, units and tables. This guide translates the Consumer Confidence Report into plain English: where to find it, what each column means, which numbers matter, and what the report cannot tell you about your own tap.

2026-09-19 · CWT Editorial Team · 7 min read

Since 1999, every community water system in the United States has been required to send its customers an annual water quality report, formally called a Consumer Confidence Report (CCR). It is one of the most useful documents a homeowner never reads — partly because it arrives as a dense table of abbreviations.

Once you know the structure, a CCR takes about ten minutes to read and answers most of the questions people have about their city water. Here is how to find yours and what to look for.

Where to Find Your Report

Utilities must deliver the CCR by July 1 each year, covering the previous calendar year. Most now deliver it electronically: a link printed on your water bill, a notice in a bill insert, or a page on the utility's website (search the utility name plus "water quality report" or "consumer confidence report"). The EPA also maintains a searchable CCR locator.

If you rent, the report goes to the account holder, but you are entitled to a copy — ask the landlord or utility. If you are on a private well, there is no CCR; see our well water testing schedule instead.

The Front Section: Source, Treatment and Notices

The first page or two usually covers:

Water source. Surface water (rivers, lakes, reservoirs) or groundwater (wells), and sometimes purchased water from a neighboring system. Source matters: surface water systems tend to have more disinfection by-products and turbidity concerns; groundwater systems more naturally occurring minerals, arsenic or radon.
Source water assessment. A summary of how vulnerable the source is to contamination.
Treatment summary. Filtration, disinfection (chlorine or chloramine), corrosion control, fluoridation.
Violations and notices. Any monitoring, reporting or health-based violation during the year must be disclosed here with an explanation. This is the most important paragraph in the report — read it first.
Required health language. Boilerplate about vulnerable populations, cryptosporidium, lead and radon. It appears in every report and does not by itself indicate a problem.

Decoding the Detected Contaminants Table

The heart of the report is a table listing every regulated contaminant that was detected. Contaminants tested for but not found are usually omitted, so a short table is good news. The columns are standardized:

Column	What it means
Contaminant	The substance measured (e.g., nitrate, lead, total trihalomethanes)
Unit	ppm (mg/L), ppb (µg/L), ppt (ng/L), pCi/L for radioactivity, NTU for turbidity
MCLG	Maximum Contaminant Level Goal — the level below which there is no known health risk. Not enforceable; often zero.
MCL	Maximum Contaminant Level — the legally enforceable limit
Level detected	The system's result, usually the highest value or a running annual average
Range	The lowest to highest result across sampling sites
Violation?	Yes or No
Likely source	Boilerplate explanation of where the contaminant typically comes from

Units trip people up. One ppm equals 1,000 ppb, which equals 1,000,000 ppt. A lead result of 3 ppb is tiny; a nitrate result of 3 ppm is well under the 10 ppm limit. Always compare the detected level to the MCL in the same unit.

Two numbers are especially worth attention. First, results that sit close to the MCL even without a violation — a running average of 70 ppb for total trihalomethanes against an 80 ppb limit, for example — indicate a system under strain. Second, any contaminant whose MCLG is zero (lead, arsenic, benzene, several others) means the health goal is none at all, so any detection merits thought about point-of-use filtration.

The Lead and Copper Section Is Different

Lead and copper are reported differently because they come from household plumbing, not the source. Utilities sample a set of high-risk homes and report the 90th percentile — the value that 90% of sampled homes fell below — alongside the action level (15 ppb for lead, dropping to 10 ppb in 2027; 1.3 ppm for copper) and the number of sites that exceeded it.

A 90th-percentile lead result of, say, 6 ppb means one in ten sampled homes had more than 6 ppb at the tap. It does not tell you what your home has. If your house predates 1988 or the report shows a 90th percentile above 5 ppb, read our guide to lead in drinking water and consider an individual test. Many reports now also include a link to the utility's lead service line inventory, where you can look up the recorded material for your address.

Unregulated Contaminants and PFAS

Many reports include a second table for unregulated contaminants monitored under the EPA's Unregulated Contaminant Monitoring Rule (UCMR). These have no MCL yet; the data is being collected to decide whether regulation is warranted. Since 2023, this is where most utilities first reported PFAS results.

Because there is no MCL column to compare against, these tables can look alarming or meaningless depending on your mood. Use these reference points: the EPA's 2024 limits for PFOA and PFOS are 4.0 ppt each, and 10 ppt for PFHxS, PFNA and GenX. Our PFAS homeowner guide explains the current status of those limits and what to do if your system reported detections.

What the CCR Does Not Tell You

A clean CCR is reassuring, but it has blind spots:

Your own plumbing. Lead, copper, and bacteria that grow in a water heater or unused pipe are not reflected in system-wide results.
Hardness. It is not regulated, so many reports omit it or bury it in a "secondary standards" table. If you want to know whether you need a softener, look for hardness in grains per gallon or mg/L, call the utility, or schedule a free in-home test.
Chloramine vs. chlorine. The report will state which disinfectant is used; this matters for aquarium owners, dialysis patients and anyone choosing a carbon filter, since chloramine requires catalytic carbon.
Taste and odor. Earthy, musty or chlorinous taste rarely corresponds to a violation.
Timing. The report covers last year. A treatment change or main break this spring is not in it.

For the full picture, pair the CCR with a one-time certified test of your own tap, then revisit the report each July for changes. Compare treatment options in our system comparison tool or browse more water quality guides.

Frequently Asked Questions

What is the difference between MCL and MCLG?: The MCLG (goal) is the level at which no known or expected health risk exists, set without regard to cost or feasibility. The MCL (limit) is the enforceable standard, set as close to the goal as technology and cost allow. When the two differ widely — as with arsenic (goal 0, limit 10 ppb) — it reflects a trade-off, not a safety guarantee.
My report lists a violation. Should I stop drinking the water?: Read the type. Monitoring and reporting violations are paperwork failures that usually pose no direct risk. Health-based (MCL or treatment technique) violations are more serious; the report must explain the potential health effects and what the utility did. If a violation involved bacteria, nitrate or a boil-water notice, the utility should have notified you at the time.
Why does the report show a range instead of one number?: Utilities sample at multiple locations and times. The range shows the lowest and highest individual results; the "level detected" is typically the highest value or the running annual average used for compliance. A wide range usually reflects seasonal changes or differences between parts of the distribution system.
How do I get a CCR for a home I am thinking of buying?: Search the local utility's website — reports are public — or request it from the utility directly. For homes on private wells, ask the seller for recent laboratory results and arrange your own certified test as part of the inspection.

Topics: consumer confidence report, water quality report, CCR, city water, tap water, MCL, water contaminants