PlainWater

Our Methodology

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Data Sources

PlainWater draws from two authoritative Environmental Protection Agency datasets to provide comprehensive drinking water quality information:

  • EPA SDWIS (Safe Drinking Water Information System): Quarterly bulk data from EPA's ECHO program covering all public water systems, their violation histories, and system characteristics. The SDWIS is the primary federal database for Safe Drinking Water Act compliance.
  • EPA UCMR5 (Fifth Unregulated Contaminant Monitoring Rule): PFAS "forever chemical" testing data from 2023-2025. UCMR5 required public water systems serving 3,300+ people to test for 29 PFAS compounds and other contaminants not yet regulated under the Safe Drinking Water Act - our extract has 10,252 tested systems, not the full 143,076 SDWIS inventory.

Processing Pipeline

We download quarterly SDWIS bulk data exports from EPA's ECHO program and merge them with UCMR5 PFAS testing results. Processing steps:

  • System profiles: Each water system's basic characteristics (type, ownership, population served, source water type) are extracted from SDWIS.
  • Violation records: All violations are classified as health-based (Maximum Contaminant Level violations, Treatment Technique violations) or monitoring/reporting violations. Health-based violations are highlighted as the higher-severity category.
  • PFAS results: UCMR5 results are merged by water system PWSID, showing each detected PFAS compound with its measured concentration and EPA health advisory level comparison.
  • Geographic aggregation: County and state views aggregate system-level data to show regional compliance patterns.
  • Contaminant profiles: Cross-system analysis shows which contaminants have been detected most widely.

Violation Classification

Violations recorded in the SDWIS database fall into two main categories, each indicating different types of compliance concerns:

  • Health-Based Violations: Maximum Contaminant Level (MCL) exceedances, Treatment Technique (TT) violations, and Surface Water Treatment Rule violations. These directly affect water safety.
  • Monitoring & Reporting (M&R) Violations: Failures to test on schedule or report results as required. These do not necessarily indicate contamination but show gaps in compliance tracking.

Population coupling (SDWIS × UCMR5)

State and county pages show SDWIS violation metrics and UCMR5 PFAS metrics side by side. Those rates do not share the same population:

  • SDWIS violation rate = systems with ≥1 recorded violation ÷ all public water systems in the jurisdiction (quarterly ECHO extract).
  • UCMR5 PFAS detection rate = systems with ≥1 PFAS detection ÷ systems tested under UCMR5 (generally serving 3,300+ people; 2023-2025 cycle).

We never divide a UCMR5 count by the full SDWIS system inventory, and we never present the two percentages as interchangeable “water quality” rates. Population served on profiles is the SDWIS sum of population_served for systems in that geography - not Census resident population, and not the UCMR5 tested subset.

PFAS detection rankings apply a minimum tested-base floor (≥10 systems) before a state can lead the chart or the primary ranking; smaller tested bases stay listed separately because a handful of samples can swing the rate sharply.

Corpus placement

Entity pages state where the entity sits in the published corpus as a computed #N of M ordinal (entity-analytical-placement):

  • Systems: national and in-state ranks use EPA SDWIS population_served descending among systems serving ≥500 people (the same cohort the sitemap advertises and the detail page indexes; ties broken by PWSID). That matches the default /systems sort within the published set.
  • Counties: national and in-state ranks use county SDWIS population served descending (ties by slug), matching /counties.
  • States: ranks use SDWIS population served descending across all jurisdictions in the extract. The /states table stays alphabetical for browsing; the ordinal is the analytical placement, not the browse row order.

Ordinals are derived live from the same SQLite extract the listings use (ROW_NUMBER over the published tables). They are not editorial grades and they do not imply water-quality safety rankings.

Limitations

  • Data reflects EPA's SDWIS and is subject to reporting delays, violations may appear weeks to months after they occur.
  • UCMR5 PFAS testing only applies to systems serving 3,300+ people; smaller systems are not included in UCMR5 data.
  • Violation records show historical compliance issues; resolved violations from years ago remain in the historical record.
  • Private wells and very small community water systems may have incomplete or no data.

Data Collection Method

EPA SDWIS data is compiled from state drinking water programs. Under the Safe Drinking Water Act, each state has primary enforcement responsibility (primacy) for its public water systems and reports compliance data to EPA. States collect water quality test results, violation notices, and system characteristics from water utilities, then submit this data to EPA through the SDWIS database. UCMR5 data is collected directly from water systems under EPA authority, systems above the population threshold are required to test and report results to EPA. We download both datasets in bulk and merge them by water system identifier (PWSID) to create unified profiles.

Update Schedule

EPA publishes SDWIS bulk data updates quarterly through the ECHO program. UCMR5 results are published on a rolling basis as testing is completed (2023-2025 testing cycle). We refresh our database when new quarterly SDWIS exports and UCMR5 results become available. Between updates, new violations and test results may not be reflected.

Not Affiliated

PlainWater is not affiliated with the Environmental Protection Agency or any federal, state, or local government agency. Data is provided for informational purposes only. Always consult your local water utility's Consumer Confidence Report (CCR) for the most current and detailed water quality information about your specific water system.

Revenue diversification readiness

This section documents what is productized today for reuse or licensing, how affiliates may appear if activated, and which alternative monetization paths are paperwork-ready. It is a readiness assessment only; nothing here activates new revenue without operator sign-off.

Downloadable and citable assets today

  • State landscape CSV at /data/sdwis-state-landscape.csv - one row per state/territory with SDWIS inventory counts, violation totals, and UCMR5 PFAS testing coverage. License: /terms (attribution required; not public domain).
  • Dataset JSON-LD on the homepage, methodology, statistics, about, privacy, terms, and selected research pages declares the same extract with isBasedOn pointing to EPA SDWIS and UCMR5 sources.
  • CiteThis boxes on home, rankings, statistics, guides, research, and entity pages for one-click attribution of specific tables and counts.
  • Per-system RSS feeds at /system/[pwsid]/feed.xml for source-vintage change notifications on saved systems (see /saved).
  • Not yet productized: no bulk API endpoint, no embeddable chart iframe product, no paid data-licensing terms page. [operator] must approve pricing, API keys, and partnership terms before any launch.

Attribution ask: when reusing the CSV or citing a table, name PlainWater as the compiler and link to the source page or this methodology. Our terms reserve rights; honest attribution supports reuse without implying EPA endorsement.

YMYL-safe affiliate placement rules (if activated)

PlainWater is a health-environment registry portal (POSTURE-B). If the operator ever enables affiliate units beyond existing disclosure prose:

  • Allowed page types: general equipment or filter comparison guides where the user is already evaluating a purchase, never adjacent to system violation records, PFAS lab results, or any page that could be read as tap-water safety advice.
  • Forbidden: health claims, filtration recommendations tied to a specific system's violation status, or affiliate links on entity detail pages, county/state profiles, or rankings tables.
  • Labeling: every paid link carries a visible affiliate disclosure; no disguised buttons inside data tables.
  • Density: same Module 36 ceilings as display ads; no affiliate block above the first source-attribution line on registry pages.

Alternative ad-network eligibility (paperwork only)

  • Google AdSense: portal is in GETTING_READY review queue; no manual ad slots are enabled pre-approval. Do not resubmit while /county/* rendered-similarity stays in the REJECT-RISK band.
  • Mediavine Journey: requires ~1,000 real sessions per 28-day window. PlainWater measured ~480 GA4 sessions in the latest 28-day window (2026-08-31), so it is not eligible today. Re-check when real sessions cross the threshold. [operator] applies to network enrollment.
  • Data licensing / API: CSV + Dataset schema are the passive product surface; any commercial API or white-label embed requires [operator] pricing, terms of use, and legal review before publication.

Official Source Links

The primary datasets and agency pages this page describes:

Download the SDWIS/UCMR5 state landscape snapshot cited on this page: sdwis-state-landscape.csv (same CSV as /statistics, CC0).