Important data quality disclaimer
Read this first. Every grade and contaminant detection on TapWaterSafety.org should be one of two things, and we mark which one on each page:
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Real data — pulled live from EPA SDWIS (Safe Drinking Water Information System), EPA ECHO (Enforcement and Compliance History Online), the EWG Tap Water Database, and the utility’s own published Consumer Confidence Report (CCR). Every utility page lists exactly which sources contributed, with links to the originals so anyone can verify our numbers.
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Illustrative / sample data — used only when a utility hasn’t been enriched with live source data yet. Sample data is shaped by source-water-type heuristics (e.g. a surface water system in an industrial area will show plausible disinfection byproducts and possible PFAS detection). Sample data is clearly labeled “Stub data” or “Sample data” in the source attribution on every page that uses it.
Do not treat sample data as if it were a real measurement of your tap water. Sample data exists to demonstrate site functionality and provide reasonable placeholder values; it is not an authoritative reading of any specific utility’s water quality. The methodology (how grades are calculated from inputs) is sound regardless of which data type is shown, but the inputs determine the output. Garbage in, garbage out.
For your specific home and water utility, the most authoritative source is always your utility’s annual Consumer Confidence Report (CCR), which we link to from every utility page. If you want lab-verified data on your specific tap, order a water test from an EPA-certified laboratory.
Where our data comes from
Every grade on this site is derived from one or more of these public, verifiable sources:
- EPA SDWIS Federal Reporting Services (epa.gov/enviro/sdwis-overview) — master list of every US public water system, including utility name, source water type, service area, owner type, and population served. Free, public, refreshed quarterly.
- EPA ECHO (echo.epa.gov) — Safe Drinking Water Act violations, compliance history, and enforcement actions. The federal record of who broke what rules and when. Free, public, refreshed quarterly.
- EWG Tap Water Database (ewg.org/tapwater) — contaminant detection levels compared against EWG’s health-based guidelines, which are typically stricter than legal limits. Maintained by the Environmental Working Group, a nonprofit. Refreshed annually.
- Utility Consumer Confidence Reports (CCRs) — each utility is legally required to publish an annual CCR with contaminant testing results. We link to these from each utility page so you can read the original.
- EPA UCMR (Unregulated Contaminant Monitoring Rule) — specifically UCMR 5 for PFAS detection data (2023-2025 sampling cycle).
- US Census Bureau ACS (census.gov/programs-surveys/acs) — population and service area demographic data.
See our data sources page for the complete list with refresh schedules and known limitations.
How affiliate funding works
TapWaterSafety earns affiliate commissions when readers click links on this site and subsequently purchase water filtration products. This is the primary way the site is funded. The Federal Trade Commission requires us to disclose this — both on a dedicated page like this one, and on every page that contains affiliate links.
Specifically, who pays us
We have affiliate relationships with the following companies. When a reader clicks through one of our links and purchases a product, we receive a commission. The reader does not pay extra — the commission comes out of the company’s marketing budget.
- Amazon Associates — typically 3-4.5% of qualifying purchases
- Clearly Filtered (direct program) — typically 15-20%
- Aquasana (via Impact Radius) — typically 8-10%
- AquaTru (via ShareASale) — flat ~$40-60 per qualifying sale
- Other filter brands — may be added as the site grows; all will be disclosed here
How affiliate income does NOT affect our editorial work
Filter recommendations on utility pages are determined by the utility’s specific contaminants and third-party NSF/ANSI certifications. The Top Concerns logic — implemented in our public scoring methodology and runnable by anyone — determines which filter category we recommend before any product is selected. We then choose specific products within that category based on certifications, independent testing data, and customer track record.
We do not modify a utility’s grade, top concerns, or recommended filter category based on what would generate more affiliate revenue. The scoring engine is published openly.
What we don’t do
We do not accept payment from filter companies in exchange for inclusion. We have declined affiliate offers from products that do not carry the third-party certifications we require. We do not run sponsored content disguised as editorial.
Why we’re transparent about this
Affiliate marketing has a reputation problem because some sites recommend whatever pays the highest commission. We can’t credibly publish a “trust us” methodology while obscuring how we make money. Showing the math openly is the only way the editorial work and the business model can both be honest.