Open data
The tables behind every page. Source data are U.S. government works (public domain); our computed columns are free to reuse with attribution to Tap by Utility.
Downloads
| File | What it is | Size |
|---|---|---|
| county-rollup.csv | Per-county counts | 166 KB |
| county-rollup.json | Same as JSON | 805 KB |
| filter-fit.json | The filter-fit table with source IDs | 8 KB |
| launch-pages.csv | The systems, counties and states that have their own page, with rank | 77 KB |
| state-rollup.csv | Per-state counts | 5 KB |
| state-rollup.json | Same as JSON | 22 KB |
| summary.json | Headline counts and dates | 2 KB |
| systems-eligible.csv | One row per water system with complete PFAS testing (8,990 rows) | 1.3 MB |
| systems-eligible.json | Same table as JSON | 4.6 MB |
| ucmr5-compound-results-eligible.csv | Per system and compound: highest result, detections, reporting level (CSV only: the JSON form is too large to host) | 14.1 MB |
Data downloaded 2026-10-26; SDWIS snapshot 2026-10-13. Not compliance determinations.
Fields
| Column | Meaning |
|---|---|
| pwsid | EPA public water system ID (2-letter state or region code + 7 digits) |
| population_served | Estimated population served, SDWIS |
| primary_source | GW, SW, GU, or purchased (GWP, SWP, GUP) |
| hb_viol_5y | Health-based violations with noncompliance period beginning on or after 2021-10-26 |
| pb90_mgl / pb90_period_end | Latest lead 90th percentile (mg/L) and end of its sampling period; may be stale |
| ucmr5_full_set | True if at least one sampling point has a full UCMR 5 set (2 results groundwater, 4 surface water) |
| pfoa_max_sp_avg_ppt … hfpo_da_max_sp_avg_ppt | Highest sampling-point average in ppt (ng/L); non-detects = 0 |
| hazard_index_max | Highest sampling-point hazard index (PFHxS, PFNA, GenX, PFBS) |
| pfas_any_mcl_exceed_epa_method | True if any compound or HI is above its level by EPA Table 4 rounding rules; screening only |
| lithium_max_ugl | Highest lithium result, µg/L |
Coverage numbers
| Active community water systems (population > 0) | 49,123 |
| Serving 3,300+ with a full UCMR 5 set (page eligible) | 8,990 |
| Of those, above a 2024 federal PFAS level at 1+ sampling points | 1,053 |