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How to Read Your Water Quality Report in 10 Minutes
Before you buy any filter, find out what's in your water. If you're on public water, your utility already tested it and published the results. This guide walks you through the report.
Key takeaways
- Community water systems publish a Consumer Confidence Report (CCR) every year, usually by July 1. The EPA links to local reports.
- MCL is the enforceable limit. MCLG is the health goal, which can be lower, even zero.
- Lead is reported differently: as a 90th percentile value compared with an action level.
- Private wells aren't covered. If you have a well, testing is up to you.
Step 1: Find your report
Search your utility's name plus “water quality report,” check your water bill, or use the EPA's Consumer Confidence Report page, which links to a lookup for local reports.[1] Community water systems are required to deliver a report to customers each year, generally by July 1, covering the previous calendar year.[2][4]
If your water comes from a private well, there's no report. Federal drinking water rules don't apply to private wells, so test through a certified lab. Your state or county health department can recommend one.
Step 2: Learn the five terms that matter
| Term | What it means | How to use it |
|---|---|---|
| MCL | Maximum Contaminant Level. The highest level allowed by law. | A result above the MCL is a violation. |
| MCLG | Maximum Contaminant Level Goal. The level with no known or expected health risk. Not enforceable. | When a result is below the MCL but above the MCLG, a filter can still make sense. |
| AL | Action Level. The trigger for required utility action, used for lead and copper. | Compare the 90th percentile to the AL. Your own tap may differ. |
| ppb / ppt | Parts per billion and parts per trillion. 1 ppb equals 1 µg/L. 1 ppt is a thousand times smaller. | Check units carefully. PFAS is reported in ppt, lead in ppb. |
| ND | Not detected at the lab's reporting limit. | Means below what the lab can measure, not necessarily zero. |
Step 3: Scan for these lines
- Violations. Reports must describe any violation and what the utility is doing about it.
- Lead. Look for the 90th percentile value and the number of sites above the action level. The action level is 15 ppb today and falls to 10 ppb on November 1, 2027. See our lead guide.
- PFAS. Many utilities now report PFOA and PFOS. The EPA's 2024 limit is 4 ppt for each.[3] See our PFAS guide.
- Nitrate and arsenic, common in agricultural or groundwater areas.
- Disinfection byproducts (TTHMs and HAA5), which form when chlorine reacts with organic matter.
- Source water. Whether your water comes from a river, lake or aquifer helps explain everything else.
Step 4: Turn the report into a filter choice
List every contaminant that's detected above its MCLG, or that you're concerned about. Then find a filter certified to reduce each of them. Our guide to NSF certifications shows how to check. If nothing stands out and you just dislike the taste, a filter certified to NSF/ANSI 42 for chlorine is usually enough.
Remember: the report reflects water leaving the treatment plant and sampling across the system. Lead and copper mostly come from plumbing inside or near your home, so a clean report doesn't rule them out. Test your own tap if your home is older.
Frequently asked questions
How often is the water quality report published?
Every year for community water systems, generally by July 1 for the prior calendar year.
My report shows a contaminant below the MCL. Is my water safe?
It meets federal law. Whether you want extra protection is a personal choice, especially when the MCLG is lower than the MCL, as it is for lead and for PFOA and PFOS, which have MCLGs of zero.
Sources
This guide is general information, not medical advice. Rules and certifications change. We last checked these sources on October 7, 2026. Found an error? Tell us and we will correct it.