Plumbing Picks is reader-supported. As an Amazon Associate, we earn from qualifying purchases at no extra cost to you.
Quick answer: Get your water supplier’s latest Consumer Confidence Report (CCR), then read the result, units, sample date and violation notes together. An MCL is an enforceable contaminant limit; an MCLG is a health goal. The reported comparison value may be a single result, an average or a percentile. The highest number in the range is not always the value used for compliance. A system-wide report also cannot tell you exactly what comes out of your own tap.
Use the report to decide what questions to ask before buying a test or filter. It describes the water supply and its monitoring results; it is not a shopping list or a guarantee for every household.
Find the Right Report First
EPA’s consumer guidance says community water suppliers must send an annual report by July 1. Ask your supplier for its latest report, or use the EPA consumer page and its report-search link (epa.gov). A renter whose water bill goes through a landlord can ask the building manager or supplier.
Check the report year, service area and sample dates. Where a supplier serves separate water systems, results may be split by area. Some substances are sampled less often than annually, so a recent report can contain older sampling dates. Read the report’s explanation instead of assuming every row was tested this year.
A household private well does not get this community-system report. EPA recommends annual well testing for total coliform bacteria, nitrates, total dissolved solids and pH, plus other substances when local conditions warrant it. Its private-well guidance (epa.gov) explains when extra tests are needed and how to find a certified drinking-water laboratory.
What the Table Terms Mean
| Term | Meaning and limit |
|---|---|
| MCL | Maximum Contaminant Level: the enforceable limit for that substance. Use the report’s compliance value and explanation. |
| MCLG | Maximum Contaminant Level Goal: a non-enforceable health goal for that substance, not a whole-water safety certificate. |
| TT | Treatment Technique: a required treatment process rather than a simple concentration limit. |
| AL | Action Level: a concentration threshold whose exceedance triggers treatment or other system requirements. It is not interchangeable with an MCL or a personal safe-exposure threshold. |
| MRDL / MRDLG | The allowed disinfectant level and its health goal. These refer to disinfectants, not every contaminant. |
| Reported level | Read its label. Depending on the substance, it can be a highest result, a running average or a percentile. |
| Range | The low and high detected results. It can show variation even when compliance uses an average. |
| Sample date | When the testing was done; it can differ from the report’s publication year. |
| Violation | Read the explanation. Violations can concern contaminant limits, treatment, monitoring or reporting. |
EPA’s illustrated report is a helpful starting point. The federal report-content rule (ecfr.gov) explains why averages, action levels and other reporting cases need their own interpretation.
Read One Row Without Mixing the Numbers
- Name the substance. Compare its result with its own limit or treatment requirement.
- Match the units. Do not compare a number in mg/L with a limit in ppb without conversion. Use the units printed for that row.
- Identify the comparison value. A range maximum and a running average answer different questions. Read the column label and footnotes.
- Read the violation explanation. Ask the supplier which result determined compliance and what any listed violation means.
- Check what applies now. Follow current instructions from the supplier or health department; an annual report describes a reporting period.
For example, federal reporting rules use locational running annual averages for TTHM and HAA5, alongside individual-sample ranges. Lead and copper reporting uses a 90th-percentile result. Calling every row’s headline number its single highest sample would miss those distinctions.
What a Good Report Cannot Tell You About Your Tap
The CCR includes system monitoring, which can include selected household samples. It does not test every home’s tap. EPA identifies lead service lines, fixtures and solder as possible sources of lead. Its health goal for lead in drinking water is zero, and it regulates lead through a treatment technique rather than an MCL.
If lead at your tap is the concern, ask your supplier or state drinking-water authority about certified laboratory testing and sampling instructions. EPA’s lead guidance (epa.gov) explains those steps. For the difference between a home screen and a mail-in test, compare our water test kit guide. A home screening kit cannot certify that water is safe.
If you later choose treatment, match it to the identified substance and the exact certified reduction claim. Our filter-certification guide explains how to check the model and replacement cartridge. A detected substance alone does not tell you which filter to buy.
Questions to Ask Your Water Supplier
- Does this report cover my address and service area?
- Is this row showing a single result, an average or a percentile?
- What does the violation or action-level note mean, and what steps should customers take?
- How can I check my service-line material and arrange a test of my own tap?
Your supplier’s contact details should be in the report. EPA also lists its Safe Drinking Water Hotline, 1-800-426-4791. For an individual health concern, ask your healthcare provider.
FAQ
Does a result below the MCL mean every tap is safe?
No. It describes compliance for that reported substance and monitoring basis. A CCR does not test every home’s tap, and household plumbing can add lead.
Is the MCLG the legal limit?
No. An MCLG is a non-enforceable health goal. An MCL is an enforceable contaminant limit; some substances use a treatment technique or action level instead.
Why is the range maximum higher than the reported compliance number?
Some substances use an average for compliance while the range shows individual samples. Read the row’s footnotes and ask the supplier which value applies.
Can private well owners use the town’s report instead of testing?
No. A community water report does not test your household well. EPA recommends annual private-well testing and additional tests when conditions warrant them, using a certified drinking-water laboratory.
Sources and Scope
Checked October 9, 2026 against the government sources below. This guide explains how to read a report; it does not interpret a particular household’s test or replace the supplier’s current instructions.
- US EPA: CCR information for consumers (epa.gov)
- US EPA: Understanding Your Water Quality Report, illustrated example (PDF) (epa.gov)
- 40 CFR 141.153: report definitions and reporting values (ecfr.gov)
- US EPA: lead in drinking water (epa.gov)
- US EPA: private-well testing (epa.gov)