How to read your annual water quality report

The most useful document about your water is published every year by the utility that delivers it, and it costs nothing to read.

Under the Safe Drinking Water Act, every community water system in the United States has to publish an annual Consumer Confidence Report — a CCR, sometimes called an Annual Water Quality Report. Central Alabama Water (formerly Birmingham Water Works) publishes theirs at caw-al.gov.

They are dense documents. But there are about six things worth understanding, and once you have them the whole thing becomes readable.

1. MCL versus MCLG — the two numbers people confuse

Every regulated contaminant is reported against two values. Keeping them apart is most of what it takes to read the table correctly.

Several contaminants have an MCLG of zero — the theoretical ideal is none at all — while the MCL is a small but non-zero number reflecting what treatment can actually achieve.

That gap is where the two get mixed up. "The EPA's health goal for this is zero, and your water has some" is technically accurate and tells you almost nothing: nearly every water system in the country reads the same way. Compliance is measured against the MCL.

2. Running annual average — why one high reading isn't a violation

For disinfection byproducts, compliance is determined on a running annual average at each sampling location — a locational running annual average, or LRAA — rather than on any single sample.

Central Alabama Water's 2026 report shows a highest TTHM LRAA of 63.3 µg/L against an MCL of 80. Comfortably compliant.

The same table publishes the range of results sitting behind those averages: 17.7 to 80.6 µg/L. The top of that range edges past 80 — as a single result, at one location, at one time.

That is how the standard is written, and for a sound reason: byproduct formation varies with temperature, water age and distance from the plant, so one spike is a poor measure of long-term exposure.

It is still useful information. It tells you byproduct levels aren't uniform, and that homes at the far end of a distribution run generally see more than homes near the plant. Your house has a number, and the system average isn't necessarily it.

3. Primary versus secondary standards

Reports split into two sections, and the difference between them is worth holding on to.

Primary standards are health-based and legally enforceable — lead, nitrate, disinfection byproducts, radionuclides.

Secondary standards are aesthetic. Taste, odor, color, staining. They are not health-based and generally not federally enforceable.

Here's the thing: the secondary table is usually where the commercially interesting numbers live.

Hardness, pH, total dissolved solids, iron, manganese, the Langelier Saturation Index — all secondary. All relevant to whether you need water treatment. None of them health issues.

4. Find your hardness — it's not where you'd expect

Hardness almost never appears in the headline section. It's in the secondary standards table, usually reported as "Total Hardness" in mg/L as calcium carbonate.

Central Alabama Water's 2026 report gives a system-wide range of 38 to 224 mg/L.

To convert to grains per gallon — the unit the softener industry uses — divide by 17.1.

38 ÷ 17.1 = 2.2 gpg. 224 ÷ 17.1 = 13.1 gpg.

That is a wide range, and it is the single most useful thing this page can hand you. Against the classification the industry uses, one published range crosses four bands:

At 2.2 gpg the water is slightly hard. At 13.1 gpg it is very hard. Both figures come from the same system in the same year, and which end of that range reaches your house depends on which source and which part of the distribution network feeds it.

So the published range is a reason to measure rather than a conclusion. It tells you the question is worth asking at your own address.

We went through what that range means for a softener decision separately, including the widely repeated "15.2 gpg" figure for Birmingham, which sits above the highest number the utility publishes. Neighboring systems — Trussville, Pelham, Alabaster — publish their own hardness figures, and those are different numbers again, so confirm which utility serves you before reading anyone's range as yours.

The bonus number almost nobody knows about

While you're in the secondary table, look for Langelier Saturation Index. It predicts whether water deposits scale or dissolves it. Positive means scale-forming; negative means the opposite.

Central Alabama Water's 2026 report lists values from −1.28 to −0.06 — negative across the system. Read that alongside the hardness range: even where hardness reaches the top of its band, the water itself is not scale-forming.

5. "ND" means not detected, not absent

ND means the contaminant wasn't found above the method detection limit for the test used. It doesn't prove zero — it means below what the instrument could measure.

Detection limits improve over time, which is why PFAS entries started appearing in these reports recently. Those compounds didn't arrive in 2023; the ability to measure them at very low concentrations did. The current report shows how this reads in practice: PFOA is listed with ND at the bottom of its range and a measured value at the top — same compound, different sample, different answer.

6. Know your source water

Near the front, every report names its sources. Central Alabama Water's are the Cahaba River, Little Cahaba, Lake Purdy, Inland Lake and the Black Warrior basin — all surface water.

That single fact predicts a lot:

• Higher organic load → more disinfection byproduct formation. Not a treatment failure; a consequence of the source.
• Seasonal taste and odor events → algae produce geosmin in spring. That's the musty water people noticed in May 2024.
• Hardness that varies with the source → a system drawing on several rivers and lakes delivers different hardness to different addresses, which is why the published range is as wide as it is.

Groundwater systems read differently — typically harder water, more iron and manganese, fewer byproducts, no algae blooms. If you're reading a report from a well-sourced system, expect a different set of numbers to matter.

A fifteen-minute exercise

1. Download your CCR. Central Alabama Water publishes theirs at caw-al.gov.
2. Find your source water. Surface or ground?
3. Find Total Hardness in the secondary table. Divide by 17.1, then find that number in the band table above.
4. Find TTHM and HAA5. Note both the highest LRAA and the range behind it.
5. Find Langelier Saturation Index if reported.
6. Check the lead 90th percentile figure.

Six numbers. Fifteen minutes. After that you know what the system delivers on average, what varies across it, and which of those numbers is worth measuring at your own tap.

That's a solid place to be standing before you spend anything on equipment.