Guide
How to read your water quality report
Where to find your utility's annual report, which rows actually matter, and what the numbers do and do not tell you about your own tap.
Finding the report
Every community water system in the United States must publish an annual Consumer Confidence Report covering the previous calendar year, normally by July 1. It is free, it is public, and most utilities put it on their website.
Search for your utility's name with the phrase water quality report, or look for it on your bill. If you do not know who supplies you, your municipality's website will say, and the EPA maintains a searchable database of public water systems.
If you are on a private well, none of this exists for you. No agency samples it and no report is produced. Our guide on city water against well water covers what to do instead.
The three numbers that matter
MCL, the maximum contaminant level, is the legal limit. A system above it is in violation and must notify customers.
MCLG, the maximum contaminant level goal, is the level at which no known health effects occur, with a safety margin. It is a health target rather than an enforceable limit, and for some contaminants it is set at zero. A result above the MCLG but below the MCL is legal and common, and it is not a violation.
The action level, used for lead and copper, is different again. It is not a health limit on your tap. It is a trigger: if more than ten percent of sampled homes exceed it, the system must take specified steps such as corrosion control and service line replacement.
Reading the table without being misled
Most reports show a range and an average. The average is often reassuring and the range is where the useful information sits, because it tells you what the worst sampling point looked like.
Check the year each figure covers. A report published this summer usually describes last calendar year, so the data is already a year old when you read it.
Units change between rows. Parts per million and parts per billion differ by a factor of a thousand, and it is easy to read a number as small when it is not.
Detected is not the same as exceeded. Modern laboratory methods find very small quantities of many things. A detection well below the limit is normal rather than alarming.
What the report cannot tell you
It describes the distribution system, not your tap. The water is sampled at points across the network, and everything that happens in the pipe between the main and your kitchen is outside its scope.
For lead this matters more than for anything else. Lead is not in the water leaving the plant. It dissolves out of the service line, out of solder in buildings plumbed before 1986, and out of brass fittings. A clean system-wide lead result tells you very little about a pre-war building with an unknown service line.
Hardness may not appear at all, because it is not a regulated contaminant. Many utilities publish it anyway as a secondary parameter, and where they do it is a system average that your own tap can differ from.
PFAS reporting is expanding under the 2024 federal limits, so a report from a few years ago may simply not have looked.
A short checklist
Confirm the disinfectant. Chlorine or chloramine, because that decides which carbon media works.
Look for any violation notices. They are required to be stated plainly.
Note the hardness figure if it is published, and compare it against what you are seeing on fixtures.
Find the lead section and read what it says about service line inventories, then look your own address up in the municipal inventory.
Check whether PFAS was monitored and what was found.
Everything else in the table can usually be read as confirmation that the system is doing its job.
Common questions
My report shows a detection above the MCLG. Should I be worried?
Not on its own. The MCLG is a health goal with a safety margin built in, and for several contaminants it is set at zero, which no real water supply achieves. The enforceable limit is the MCL. A result between the two is legal and extremely common. What is worth attention is a result close to the MCL, a rising trend across years, or an actual violation notice.
The report says lead was not detected. Does that mean my water is safe?
It means the sampled homes were mostly fine, which is useful but not about your tap. Lead enters from the service line and the plumbing inside your building, so the result depends on your address rather than the system. If your building predates 1986 or the service line inventory lists lead or unknown, test your own tap.
Why does my water taste different at different times of year?
Several reasons, all normal. Utilities sometimes switch disinfection seasonally. Reservoir water changes with temperature and rainfall, and algal activity in summer can produce an earthy taste that is harmless. A system drawing from more than one source may shift the blend. If the change is sudden and severe rather than gradual, call the utility, because they usually know already.
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