How to read a municipal water quality report without losing your mind

Every U.S. community water system is required by the EPA to publish a Consumer Confidence Report (CCR) once a year. It lists detected contaminants, the regulatory limit for each one, and the level your utility measured. On the surface it’s a tidy table. Underneath, it papers over three things that matter.

1. “Below the regulatory limit” is not the same as “safe”

The EPA’s Maximum Contaminant Levels (MCLs) for a number of common compounds — lead, arsenic, chromium-6 — were set decades ago and reflect what was technically and economically feasible to enforce at the time, not what current health data would recommend. The California state EPA’s public health goals for some of these contaminants are 10× to 1,000× lower than the federal MCL. A report that says your tap water is “in compliance” is telling you it’s legal. It is not telling you it’s clean.

2. Disinfection by-products are usually the bigger story

Most public reports lead with lead and copper because those are politically charged. The contaminants more likely to show up in your specific glass of water at meaningful levels are the disinfection by-products — total trihalomethanes (TTHM) and haloacetic acids (HAA5). TTHM is the regulated sum of four compounds (chloroform plus three brominated relatives) with an MCL of 80 µg/L. HAA5 is the regulated sum of five haloacetic acids with an MCL of 60 µg/L. Compliance is evaluated as a locational running annual average over quarterly samples, which means an individual reading can spike well above the limit and the system still stays “in compliance” if the four-quarter average is under. These are formed when chlorine reacts with organic matter in the source water — the more organic matter (often from agricultural runoff or surface water), the more by-products.

3. Per- and polyfluoroalkyl substances (PFAS) are mostly not in the report

The EPA finalized national PFAS drinking water standards in April 2024 — Maximum Contaminant Levels for six compounds including PFOA and PFOS. The original compliance deadline was 2029, but in May 2025 the EPA pushed the PFOA and PFOS deadline out to 2031, giving utilities two extra years before they have to meet the limits. Your CCR may or may not include PFAS data depending on what year you’re reading and whether your utility has been required to test. If the report is silent on PFAS, that doesn’t mean they’re absent — it means they weren’t measured.

What to actually do with the report

• Look up your utility’s full report (search “[utility name] consumer confidence report”).
• Find the disinfection by-products section first. Compare against California’s public health goals, not the federal MCL.
• Search for “PFAS” or “perfluoro” in the document. If absent, check your state’s PFAS dashboard.
• Then decide what level of filtration is appropriate. The water filtration category is sorted by what the systems actually reduce, not by what they advertise.

The point is not to alarm. The point is that “compliant” is a regulatory verdict, not a clean-water verdict, and the two should not be conflated.