A violation label is not a shopping list

EPA's own contaminant codes name a specific rule or chemical - "Surface Water Treatment Rule," "TTHM," "Nitrate" - not a product. DrinkingWaterCheck groups the 66 distinct labels that actually appear in this dataset into a handful of concern categories, each pointing at a different class of home filter, because that is the decision the label is actually useful for.

Lead & copper: a pitcher filter is not enough

Lead contamination is almost always from the plumbing between the water main and the tap, not the treated water itself, so it needs a filter certified to NSF/ANSI 53 for lead, not a basic carbon pitcher certified only for taste. CHICAGO, IL's page shows what a lead & copper flag looks like on a real system's record.

Microbial and disinfection-byproduct flags: different fixes

A microbial or treatment-technique violation (total coliform, a lapsed disinfection or filtration step) calls for a filter certified for cysts and bacteria, not carbon alone. Disinfection byproducts like TTHM are the opposite case - a standard carbon filter handles them well, since the concern is long-term chemical exposure rather than an acute pathogen. NEW YORK CITY SYSTEM, NY is a large system where a microbial-category flag is on record.

Nitrate, radionuclides, and other regulated metals

Nitrate, radionuclides, and most other regulated metals (arsenic, chromium, fluoride) pass straight through carbon filters and need reverse osmosis instead, since these are dissolved inorganic compounds, not organic chemicals carbon adsorbs. COLUMBUS PUBLIC WATER SYSTEM, OH is a real system with a nitrate flag on record. Every system's own page names its specific flagged category and the filter class it points to, next to its violation history.

Where to go next

Real systems this plays out on: CHICAGO, IL, NEW YORK CITY SYSTEM, NY, COLUMBUS PUBLIC WATER SYSTEM, OH.

Why Lead Violations Get Treated as the Most Urgent Category · What EPA's Water Data Doesn't Cover