How to Read Your Water Quality Report (Consumer Confidence Report)

Your water quality report, officially called a Consumer Confidence Report (CCR), is a yearly summary your water utility must send you by July 1. To read it, find the table of detected contaminants and compare three numbers in each row: the level found in your water, the MCL (the legal limit), and the MCLG (the health goal). Then check the “Violation” column and the separate violations section. If every row says “No” and the levels sit below the MCL, your utility met federal standards for that year.

That is the short version. The rest of this guide explains each term so you can tell the difference between “legal” and “ideal,” and spot the rows worth a closer look.

What a CCR is and how to get one

EPA requires every community water system to deliver a CCR to its customers each year by July 1. It covers the previous calendar year of testing. According to EPA, each report includes:

Where your water comes from (a river, lake, aquifer or other source) and a summary of contamination risks to that source
Regulated contaminants detected in your water
Possible health effects of any contaminant found in violation of an EPA standard, and what the utility is doing about it
An educational statement for people with weakened immune systems about Cryptosporidium
Information on nitrate, arsenic or lead where those may be a concern
Contact numbers, including EPA’s Safe Drinking Water Hotline (1-800-426-4791)

Many utilities post the report on their website or link to it from your bill. EPA also has a Find your local CCR lookup. If you rent, your landlord or building manager may receive the report; you can ask the utility directly for a copy.

Changes are coming. In May 2024, EPA finalized revisions to the CCR rule. Starting in 2027, reports must be easier to read, support translation into appropriate languages, and include more information about lead. Systems serving 10,000 or more people will have to send reports twice a year instead of once.

The key terms

These definitions come from EPA’s National Primary Drinking Water Regulations.

MCLG (Maximum Contaminant Level Goal): “The level of a contaminant in drinking water below which there is no known or expected risk to health.” This is a health goal, not a legal limit. For contaminants linked to cancer, such as arsenic and radium, and for lead, the MCLG is zero.

MCL (Maximum Contaminant Level): “The highest level of a contaminant that is allowed in drinking water.” This is the enforceable legal limit. EPA sets MCLs as close to the MCLG as it considers feasible, which is why an MCL can be higher than the MCLG.

MRDL and MRDLG: the same idea as MCL and MCLG, but for disinfectants such as chlorine and chloramine. EPA’s MRDL for chlorine is 4.0 mg/L. Learn more in our chlorine and chloramine guide.

TT (Treatment Technique): “A required process intended to reduce the level of a contaminant in drinking water.” EPA uses a TT instead of an MCL when it is not practical to measure a contaminant directly. Germs like Cryptosporidium are controlled this way, and so is turbidity (cloudiness), which many reports show as a TT row.

AL (Action Level): the concentration of a contaminant which, if exceeded, triggers treatment or other actions the water system must take. Lead and copper use action levels. The lead action level is 15 ppb (0.015 mg/L). Under EPA’s 2024 Lead and Copper Rule Improvements, as published, it drops to 10 ppb starting November 1, 2027; check EPA’s rule page for the current status. Copper’s is 1.3 mg/L.

Units: ppm, ppb, ppt

Reports mix units, which makes rows hard to compare. Here is the key:

Unit	Also written as	Meaning
ppm	mg/L	parts per million
ppb	µg/L	parts per billion (1 ppm = 1,000 ppb)
ppt	ng/L	parts per trillion (1 ppb = 1,000 ppt)
pCi/L		picocuries per liter, a measure of radioactivity (radium, gross alpha)

So an arsenic MCL of 0.010 mg/L is the same as 10 ppb. PFAS are reported in ppt; EPA’s limit for PFOA and PFOS is 4.0 ppt. Always check that the level and the MCL in a row use the same unit before comparing.

How to read the main table

Most CCRs have a table of regulated contaminants with columns like these. The numbers below are made up for illustration, not from any real utility:

Contaminant (unit)	MCL	MCLG	Level detected	Range	Violation	Likely source
Nitrate (ppm)	10	10	2.1	0.4 to 3.8	No	Fertilizer runoff
Total trihalomethanes (ppb)	80	n/a	52	21 to 74	No	Byproduct of disinfection
Arsenic (ppb)	10	0	4	ND to 7	No	Erosion of natural deposits

Level detected is usually the highest average or highest single result used to judge compliance. It is not always the worst sample. For trihalomethanes and haloacetic acids, compliance is based on a running annual average at each monitoring location, so one high quarter can be averaged out.

Range shows the lowest and highest individual results. “ND” means not detected. Look here if the main number seems low: a range that peaks close to the MCL deserves attention.

Likely source is the utility’s general explanation of where that contaminant usually comes from.

MCLG gaps. In the example, arsenic is legal at 4 ppb, but the health goal is zero. Many contaminants are legal yet above their health goal or stricter guidelines. That gap is why TapWaterSafety also compares levels with stricter benchmarks. See EWG vs. EPA: the gap and California’s public health goals.

The lead and copper section

Lead and copper are reported differently because they come mostly from home plumbing, not the source. Instead of an average, your report shows:

The 90th percentile result from the most recent round of tap samples. Nine in ten homes tested were at or below this number.
The number of sites above the action level
Often, the range of individual results

If the 90th percentile is above the action level, EPA calls that an action level exceedance. That triggers required steps such as public education and corrosion control. A low 90th percentile is good news for the system, but it says nothing certain about your own pipes. Only a test at your tap can do that. See lead in tap water and how to find out if you have a lead pipe.

The violations section

A “Yes” in the violation column, or a separate violations section, means the utility did not meet a rule. There are two broad types:

Health-based violations: a contaminant exceeded an MCL or MRDL, or the utility did not follow a required treatment technique. The report must explain possible health effects and what the utility is doing to fix it.
Monitoring and reporting violations: a required test, report or notice was late or missing. This does not mean the water was contaminated, but it means there is a gap in what is known.

Read the explanation carefully: when it happened, whether it is resolved, and whether any action was needed on your part. You can also check your utility’s EPA compliance history through the EPA report linked on its TapWaterSafety page. Our post on EPA serious violators explains how EPA flags systems with repeated problems.

Unregulated contaminants and PFAS

Many reports include a table of “unregulated” contaminants. These are substances EPA is studying through its Unregulated Contaminant Monitoring Rule (UCMR). They have no MCL, so there is nothing to “violate.” The most recent round, UCMR 5, required sampling for 29 PFAS and lithium between 2023 and 2025. EPA released the final UCMR 5 dataset in August 2026.

EPA’s April 2024 PFAS rule sets enforceable limits for PFOA and PFOS, with monitoring due by 2027 and treatment required by 2029. In May 2026 EPA proposed rescinding limits for several other PFAS and allowing some systems until 2031 to meet the PFOA and PFOS limits. As of October 2026 those changes were still proposals. See our EPA PFAS rule explainer.

A five-minute checklist

Find the source. River, reservoir or wells? This hints at likely issues. See groundwater vs. surface water.
Scan the Violation column for any “Yes.”
Compare each level and range with the MCL, using matching units.
Note any rows above the MCLG. Legal does not always mean ideal.
Check the lead 90th percentile, then think about your own home’s pipes.
Read the unregulated contaminants table for PFAS results.
Call the utility with questions. The number is in the report.

If you are pregnant, preparing infant formula, or have a weakened immune system, ask your doctor how the results apply to you. Our guide to tap water for baby formula covers infants specifically.

See your utility’s summary

TapWaterSafety pulls together EPA compliance records and contaminant data for 1,000 large public water systems, each serving roughly 50,000 people or more. Search your ZIP code to see your utility’s grade, top concerns and EPA record next to your CCR.