How TapGraded Grades Work: A Report Card for Your Water System

Every active community water system in the United States gets a report card from us: one letter, A through F. Unlike your seventh-grade report card, this one comes with its work shown — every deduction traces back to a public EPA record, and the full methodology publishes the exact rubric with a worked example. The goal is to make a large, technical federal dataset legible without dumbing it down or dramatizing it. This post is the classroom version, with the actual point values.

Every system starts with an A+

Scoring begins at 100 points, and the only direction from there is down. Four things take points off, and they are not weighted equally — the rubric is built so that actual health exceedances hurt a lot more than paperwork stumbles.

Health-based violations (the exam grades)

A health-based violation means a system exceeded a Maximum Contaminant Level, a disinfectant-level limit, or missed a treatment-technique requirement under the Safe Drinking Water Act — the federal law that sets the rules of this whole exam. Within the last five years:

−15 points for each unresolved health-based violation
−8 points for each resolved one
Capped at −45 points total — a system can have a rough record, but it can’t score negative-300 no matter how chaotic the filing cabinet gets.

Monitoring and reporting violations (the late homework)

−2 points each, capped at −10 total.

A missed test or a blown reporting deadline is the water world’s late homework — worth points off, but not the same as failing the exam. There’s a catch that keeps this honest, though: a system that never tests can never exceed a limit on paper. That’s exactly why the grade treats missing data as missing (more on that below), and why these lapses cost something rather than nothing. Violations the EPA files under “Other” are counted in this bucket too.

Lead (scored on a curve nobody enjoys)

Lead is scored from the system’s latest Lead and Copper Rule 90th-percentile result, against the 15 ppb federal action level and two stricter internal thresholds:

−25 points at or above 15 ppb
−15 points from 10 up to 15 ppb
−8 points from 5 up to 10 ppb
No deduction under 5 ppb

PFAS (the new subject on the syllabus)

PFAS results come from the EPA’s UCMR5 national monitoring program, scored against the federal PFAS limits:

−20 points if any tested PFAS result is at or above its Maximum Contaminant Level
−8 points if PFAS was detected at all, even with every result under its MCL
No deduction if nothing was detected

The unaddressed-violation penalty

One more: −10 additional points if the system currently has any health-based violation the EPA lists as Unaddressed — a flat penalty on top of the health-violation deductions, and unlike the five-year windows above, it looks at the system’s status right now. Think of it as the difference between “failed a test once” and “still hasn’t turned in the make-up work.”

From points to a letter

The remaining score, clamped to 0–100, maps to the letter:

A: 90–100
B: 80–89
C: 65–79
D: 50–64
F: below 50

What the grade deliberately leaves out

Three boundaries matter as much as the rubric itself.

Only community water systems are graded — the utilities that serve residents year-round. Schools with their own wells, campgrounds, and other transient systems are out of scope, because a rubric tuned for full-time utilities would mislead if stretched over them.

Absence of data is never scored as “clean.” If a system has no reported result for a measure, the grade says so instead of quietly counting it as a pass. A blank line on a report card is not an A.

The grade describes the system, not your house. This one is serious, so no jokes here: lead usually enters water from household plumbing — your service line, your solder, your fixtures — after the water leaves the system the grade describes. No system-level score can see your pipes. A certified tap test is the only way to know your own number, and our contaminant pages explain what the system-level lead data does and doesn’t tell you.

Check our work — please

Every deduction above comes from public EPA records: violation and enforcement data from the EPA’s ECHO downloads, lead and PFAS results from the corresponding federal datasets, all listed on our data sources page. The point values, caps, and thresholds are published in full, which means anyone with a spreadsheet and an afternoon can rebuild any grade from scratch. The same data drives the rankings.

If a grade looks wrong, that transparency makes it checkable: email contact@tapgraded.com with the system’s name or PWSID and what looks off, and we’ll re-run it against the source records. And once you’ve looked up your own system — if it earned its A, feel free to raise a glass. Tap water, obviously.

Sources

TapGraded — “How the Tap Grade Works (Methodology)” — https://tapgraded.com/methodology
US EPA — “Safe Drinking Water Act (SDWA)” — https://www.epa.gov/sdwa
US EPA — “ECHO — Drinking Water Data Downloads” — https://echo.epa.gov/tools/data-downloads