How We Grade Your Water

Transparent, reproducible methodology using publicly available EPA data. Every score is computed from five weighted subscores — no black boxes, no hard caps.

Open Methodology EPA Data Only

Scoring Overview

The WaterVerge Score: 0–100

Every city receives a composite score from 0 to 100, built from five independently calculated subscores. Each subscore starts at its maximum value and deductions are applied based on the data. There is no hard cap — cities with clean records earn high grades regardless of data availability.

45 Violations max 45 pts

20 Lead & Copper max 20 pts

20 Contaminants max 20 pts

10 Compliance max 10 pts

5 Source Risk max 5 pts

100 Total Score

Interactive Tool

Score Calculator

Drag the sliders to see how each subscore affects the final grade. Try the preset scenarios to understand how different water quality profiles produce different grades.

Violations45/45

Starts at 45. Deducted for health-based and monitoring violations.

Lead & Copper20/20

Starts at 20. Deducted based on lead/copper levels.

Contaminants20/20

Starts at 20. Covers PFAS, chromium-6, HAA5, and more.

Compliance10/10

Starts at 10. Based on violation resolution rate.

Source Risk5/5

Groundwater = 5, Surface = 4, Unknown = 4.

100.0

out of 100

452020105

45 + 20 + 20 + 10 + 5 = 100.0

Subscore 1 of 5

Violation History

45 pts

The largest factor in any city's grade. We analyze every violation on record in EPA's SDWIS database for water systems serving the city. Each violation is weighted by type, severity, recency, and resolution status. Cities with no violations receive a full 45/45.

Base Deductions by Type

Health-based violations -6 pts each

MCL exceedances, treatment technique failures

Monitoring violations -2 pts each

Missed sampling, late reporting

Severity Multiplier

Significant Non-Compliance (SNC) 2x multiplier

Doubles the base deduction for the most serious infractions

Standard violations 1x (no multiplier)

Resolution Credit

Resolved violations 50% reduction

Systems that fix problems are rewarded with a halved deduction

Unresolved violations Full deduction

Recency Decay Weights

Recent violations carry more weight. Older violations decay over time but never fully disappear from the record.

≤ 1 yr 100%

≤ 3 yr 70%

≤ 5 yr 40%

≤ 10 yr 15%

> 10 yr 5%

Subscore 2 of 5

Lead & Copper

20 pts

Based on the most recent 90th percentile lead measurement from Lead and Copper Rule (LCR) sampling. Deductions increase as levels approach and exceed the EPA action level of 15 ppb. Lead data older than 6 years incurs a -1 staleness penalty. No LCR data at all = 17/20 (a small -3 penalty, not catastrophic).

0 - 3 ppb 0 pts

3 - 6 ppb -2 pts

6 - 9 ppb -4 pts

9 - 12 ppb -7 pts

12 - 15 ppb -10 pts

15 - 30 ppb -14 pts

30+ ppb -18 pts

EPA Action Level: 15 ppb

There is no safe level of lead exposure. Even levels below the EPA action level can pose health risks, especially for children and pregnant individuals.

Subscore 3 of 5

Contaminants

20 pts

A combined subscore evaluating PFAS (UCMR 5), legacy and Phase 4 unregulated contaminants from every UCMR round (1–5), industrial proximity (Superfund + TRI within 10 miles), and contaminant-specific violation history. Scoring v4 (current) caps each individual analyte at -3 pts and applies a recency multiplier per UCMR round so older rounds carry less weight.

PFAS — UCMR 5 (up to -10)

1-2 compounds detected -1.5 pts

3-5 compounds detected -3 pts

1 MCL exceedance -2.5 pts

3+ MCL exceedances -5 pts

No PFAS data -1.5 pts

PFAS aggregate is exempt from the per-analyte cap since it already pools 29 compounds.

Legacy + Phase 4 analytes (per-analyte capped, recency-discounted)

Chromium-6 > 10 µg/L (UCMR3) -2 × 0.6 = -1.2 pts

1,4-Dioxane > 0.35 µg/L (UCMR3) -1.5 × 0.6 = -0.9 pts

HAA5 > 60 µg/L (UCMR4) -1.5 × 0.8 = -1.2 pts

Manganese > 50 µg/L (UCMR4) -1 × 0.8 = -0.8 pts

Strontium > 1500 µg/L (UCMR3) -1 × 0.6 = -0.6 pts

NDMA > 10 ng/L (UCMR2) -2 × 0.3 = -0.6 pts

Perchlorate > 15 µg/L (UCMR1) -1.5 × 0.2 = -0.3 pts

Vanadium > 21 µg/L (UCMR3) -0.75 × 0.6 = -0.45 pts

Chlorate > 210 µg/L (UCMR3) -0.75 × 0.6 = -0.45 pts

Molybdenum > 40 µg/L (UCMR3) -0.5 × 0.6 = -0.3 pts

Cobalt detected (UCMR3) -0.25 × 0.6 = -0.15 pts

Lithium detected (UCMR5) -0.25 × 1.0 = -0.25 pts

Recency multipliers (v4): UCMR1 = 0.20×, UCMR2 = 0.30×, UCMR3 = 0.60×, UCMR4 = 0.80×, UCMR5 = 1.00×. Per-analyte cap = -3 pts.

Industrial Proximity (up to -3)

5+ Superfund sites within 10 mi -1.5 pts

2-4 Superfund sites within 10 mi -1 pt

1 Superfund site within 10 mi -0.5 pts

TRI ≥ 100K lbs/yr to surface water -1.5 pts

TRI ≥ 10K lbs/yr to surface water -1 pt

TRI ≥ 1K lbs/yr to surface water -0.5 pts

Computed via haversine join from EPA Superfund NPL (1,379 sites) + EPA TRI 2023 (21,849 facilities).

Contaminant Violations (up to -4)

Arsenic violations -1 pt each (max -2)

Based on EPA rule code 332

Nitrate violations -1 pt each (max -2)

Based on EPA rule code 331. Full weight (current SDWIS data, no recency discount).

Missing data handling

Cities without PFAS data receive a -1.5 point penalty. Cities with no contaminant data at all receive 17/20 (a 3-point penalty). This replaces the old grade cap system that unfairly capped small cities at D+.

Methodology versions

v2 (Phases 1–3): Five subscores, no per-analyte cap, no recency discount. v3 (Phase 5a): Added Phase 4 analytes (NDMA, perchlorate, vanadium, chlorate, molybdenum, cobalt, lithium) and Superfund/TRI proximity. v4 (Phase 7a — current): Per-analyte penalty cap of -3 pts, plus per-round UCMR recency multiplier so older monitoring rounds (e.g. UCMR1 from 2001-2005) carry proportionally less weight than current PFAS data. Each city's stored scoring_version reflects which version computed its grade.

Subscore 4 of 5

Regulatory Compliance

10 pts

Rewards water systems that demonstrate a track record of resolving violations promptly. Based on the overall resolution rate.

≥ 95% resolved 10/10 pts

80-94% resolved 8/10 pts

60-79% resolved 5/10 pts

40-59% resolved 3/10 pts

< 40% resolved 0/10 pts

Subscore 5 of 5

Source Risk

5 pts

A small bonus based on the primary water source type. Groundwater is naturally filtered and typically requires less treatment, earning a higher score. This data is available for all systems in SDWIS.

Source Type Scores

Groundwater (GW/GWP) 5/5 pts

Surface water (SW/SWP) 4/5 pts

GW under influence (GU) 3.5/5 pts

Unknown/missing 4/5 pts

Why Source Matters

Groundwater is naturally filtered through soil and rock layers, removing many contaminants before it reaches the water supply. Surface water sources (rivers, lakes, reservoirs) are more exposed to agricultural runoff, industrial discharge, and environmental contamination, requiring more extensive treatment.

Grade Scale

Score to Letter Grade

The five subscores are summed for a final score of 0-100, then mapped to a letter grade. There is no grade capping — the score you earn is the score you get.

A+

95-100

90-94

A-

85-89

B+

80-84

75-79

B-

70-74

C+

65-69

60-64

C-

55-59

D+

50-54

45-49

0-44

Data Quality

Data Confidence Indicator

Instead of capping grades based on data availability, we display a data confidence badge on each city page. This tells you how much data informed the score — without penalizing cities for data they cannot control.

High confidence

Has violation data + LCR data + contaminant data (PFAS or UCMR3/4)

Moderate confidence

Has 2 of 3 data categories

Limited confidence

Has 1 or fewer data categories

Why we removed grade capping

Under the previous system, a small city with perfect water quality and zero violations could score no higher than D+ simply because UCMR5 doesn't cover systems serving fewer than 10,000 people. The data confidence badge communicates the same transparency without distorting the grade.

Worked Example

How a Score is Calculated

Here's a step-by-step breakdown showing how a typical city's score might be calculated.

Example City, TX

Population: 250,000 · Groundwater

B+ 82.0 / 100

Violations: 39/45

Start at 45. 2 health-based violations (within 3 years, resolved): 2 × 6 × 0.7 × 0.5 = -4.2. 1 monitoring violation (5 years ago): 2 × 0.4 = -0.8. Total deduction: -5.0 → 40.0

Lead & Copper: 16/20

Start at 20. Lead 90th percentile = 7.5 ppb (ratio 0.50): -4 pts. Copper below 0.5 ratio: no deduction. Data from 2023 (fresh): no staleness penalty. → 16.0

Contaminants: 16/20

Start at 20. PFAS: 3 compounds detected (-3.0), no exceedances. Chromium-6 at 3 µg/L (-0.5). HAA5 at 25 µg/L (-0.25). No arsenic/nitrate violations. → 16.25 → 16.0

Compliance: 5/10

3 total violations, 2 resolved (67% resolution rate). 60-79% bracket → 5.0

Source Risk: 5/5

Groundwater system → 5.0

40.0 + 16.0 + 16.0 + 5.0 + 5.0 = 82.0 Grade: B+

Transparency

Data Sources & Freshness

All WaterVerge grades are derived from publicly available federal datasets. We do not use proprietary data or undisclosed adjustments.

EPA SDWIS

Safe Drinking Water Information System. Primary source for violation history, water system profiles, and compliance records.

Updated quarterly EPA SDWIS Portal

UCMR 3, 4, & 5

Unregulated Contaminant Monitoring Rules. UCMR5 provides PFAS data, UCMR3 covers chromium-6, strontium, 1,4-dioxane, and UCMR4 covers HAA5, manganese.

Updated 2-3x per year epa.gov/dwucmr

Lead & Copper Rule

90th percentile sampling results for lead and copper, collected by water systems under EPA's Lead and Copper Rule requirements.

Sampling every 1-9 years epa.gov LCR

See the methodology in action

Look up any city to see its full score breakdown, contaminant data, and violation history.

Check your city's grade Learn about WaterVerge