How to Read Your Water Quality Report

Triangle Waterworks · informational guide

Direct answer: Your utility mails an annual Consumer Confidence Report (CCR) by July 1, covering the previous calendar year, naming where your water comes from and every regulated contaminant it detected against a legal limit. Reading it means knowing MCL, MCLG, and MRDL, ppb versus ppm, and that a system-wide average isn't a promise about your kitchen tap — the gap an all-in-one system's carbon stage is built to close.

What is a Consumer Confidence Report, and when should I get mine?

A Consumer Confidence Report — usually shortened to CCR — is the annual drinking water quality report every community water system must deliver to its customers. EPA requires delivery by July 1 each year, and the report covers calendar-year data from the year before, so the CCR that arrives in a given summer reflects testing done the previous year, not the current one. It states where your water comes from — an aquifer, a lake, a river, or another source — and lists the regulated contaminants the system detected along with their levels. EPA finalized a set of CCR Rule Revisions on May 15, 2024; starting in 2027, reports must become easier to read, support translations, and include enhanced information about lead.

What do MCL, MCLG, and MRDL mean?

These three abbreviations do most of the work on a CCR, and mixing them up is the most common reading mistake. The Maximum Contaminant Level (MCL) is the enforceable legal limit for a contaminant in drinking water — the number a utility has to stay under. The Maximum Contaminant Level Goal (MCLG) is a separate, non-enforceable public health goal, usually set lower than the MCL, representing the level below which there's no known or expected health risk. The Maximum Residual Disinfectant Level (MRDL) is a related but distinct figure: the highest level of a disinfectant — chlorine or chloramine — allowed in the water. EPA sets that limit at 4.0 mg/L (as Cl2) for both chlorine and chloramine. A residual at or under that level is maintained deliberately, all the way through the distribution system, so treated water stays safe by the time it reaches a tap — that's a feature of public water, not a compliance problem to worry about.

What's the difference between ppb and ppm, and why does it matter?

Both are units of concentration, and CCRs use them depending on the contaminant. Parts per million (ppm) is the same measurement as milligrams per liter (mg/L) — the unit MRDLs are expressed in. Parts per billion (ppb) is a thousand times smaller: 1 ppm equals 1,000 ppb. Contaminants that matter in vanishingly small amounts, like PFAS, are sometimes reported in parts per trillion (ppt) — a thousand times smaller again. When you compare a number on a CCR to a limit, check that both figures use the same unit before drawing a conclusion; a reading in ppb can look larger than it is next to a limit expressed in ppm if you don't convert first.

Why does my report show a range instead of one number for my house?

Because a CCR reports for an entire system, not a single address. Utilities test at multiple points across the distribution network throughout the year, so many line items show a range — a low and a high reading — or an annual average rather than one fixed number. That's a structural feature of a system-wide report: it tells you what the utility measured across its service area, not what's running through the specific line to your house. Two homes on the same system can see modestly different results depending on plumbing age, location in the network, and how long water sits before it's used.

What do Raleigh's and Cary's reports actually show?

Reading a real line item is easier with real numbers. Raleigh Water's reporting shows haloacetic acids (HAA9) at 19.9 ppb and total trihalomethanes (TTHM) at 21.7 ppb. Cary's system, drawing from Jordan Lake, runs higher: HAA9 at 27.5 ppb and TTHM at 38.2 ppb, plus PFOA at 2.86 ppt and PFOS at 3.79 ppt. Cary's report lists 13 contaminants total above EWG's non-regulatory guidelines. Every one of these figures is compliant with EPA's legal limits — none represents a violation. EWG's guidelines sit well below the legal limits and represent a stricter, non-regulatory health benchmark, not a second legal bar. The two numbers answer different questions: the legal limit asks whether the water is safe to distribute, and the EWG guideline asks how far below the strictest precaution a reading falls. Keep them separate — a figure that's fully compliant with the first can still sit far above the second, which is what the table below shows.

What can't a water quality report tell me?

A CCR is accurate as far as it goes, but it has real limits. Hardness — the calcium and magnesium behind scale — isn't a federally regulated contaminant, so it may or may not appear on a report at all, and there's no consistent format when it does. The report also describes water at the treatment plant and across the distribution system, not what happens between the meter and a faucet; it can't account for a home's own plumbing, water heater, or how long water sits in a pipe before use. PFAS reporting is limited, too — a report that lists PFOA and PFOS numbers is telling you about those specific compounds, not the full universe of contaminants a household might care about. None of that makes the report wrong. It just means a CCR describes the water leaving the plant, not necessarily what shows up in a glass at the tap.

Where does the rest of the picture come from?

The gap between a compliant report and what you'd actually choose for your own water is exactly why Triangle Waterworks pairs a carbon stage with a softening stage in one all-in-one system for city water customers. Activated carbon addresses the things a CCR shows as compliant but doesn't erase at the tap — chlorine and chloramine taste, and disinfection byproducts like HAA9 and TTHM. A free water analysis fills in what a report can't: what's actually happening at your specific tap, right now.

Frequently Asked Questions

What's the difference between MCL and MCLG on my report? The MCL is the enforceable legal limit a utility must stay under; the MCLG is a non-enforceable public health goal, typically set lower, representing the level with no expected health risk. A CCR usually lists both side by side for regulated contaminants.

My CCR shows a range instead of one number — does that mean my water sometimes goes over the legal limit? Not necessarily. A range usually reflects multiple sampling points and times across the system over the year, not a single reading spiking above the limit. Compare the high end of the range to the MCL to confirm compliance, and remember the range describes the system, not necessarily your specific tap.

I found PFOA listed on my Cary water report — what does that number mean? Cary's report shows PFOA at 2.86 ppt, one of 13 contaminants above EWG's stricter, non-regulatory guideline, while still compliant with EPA's legal limit. A carbon stage certified for PFAS reduction, paired with softening in an all-in-one system, addresses it directly at your tap.

Where can I find my community's actual CCR online? Your utility publishes its CCR on its own website — search "[your utility name] Consumer Confidence Report" or check the utility's water quality page directly for the current year's document.

Does the report tell me whether my water is hard? Not reliably. Hardness isn't a federally regulated contaminant, so it may be absent from a CCR entirely or reported inconsistently when it does appear. A home hardness test — a test strip kit, a titration kit, or an accredited lab test — is a more direct way to find your number.

What's the difference between ppm and ppb? Parts per million (ppm) is the same unit as milligrams per liter, the unit used for MRDLs. Parts per billion (ppb) is a thousand times smaller. Always check which unit a figure uses before comparing it to a limit expressed in a different one.

Ready to see what's happening at your own tap?

A CCR tells you about the water leaving the treatment plant. To find out what's actually at your tap, take our 60-second water quiz to find the system that fits your home, or request a free water analysis for a direct, on-site read on your specific water.

Related reading: Is Cary, NC Water Safe to Drink? | Haloacetic Acids in Drinking Water | Trihalomethanes in Tap Water | How to Remove PFAS From Water | Raleigh Water Hardness