Source hierarchy
Local data pages prioritize authoritative public sources, including USGS, EPA, Census, utilities, and state or local agencies. Guides prefer primary government, standards-body, or research sources for factual and health-related claims.
Derived information
Medians, ranges, percentages, classifications, and geographic associations are labeled as derived values. The methodology must be reproducible from the retained inputs. Missing measurements are not converted to zero, pass, or a confident safety claim.
Research comparisons use a stricter subset than local pages: source-aligned observations must meet stated recency, distance, site-count, confidence, and comparability checks. A local value can therefore be published with a limitation while remaining ineligible for a ranking.
Health and safety language
Content distinguishes hardness and aesthetic concerns from health-based contaminant standards. Utility-wide compliance history is not represented as a result from an individual tap. Current official notices take precedence over summaries on this site.
Commercial independence
Affiliate eligibility does not determine hardness thresholds, data inclusion, compliance wording, or whether a treatment type is discussed. Sponsored links use appropriate relationship labels. Products are not presented as substitutes for testing when the problem is unconfirmed.
Corrections
Corrections are evaluated against authoritative evidence and propagated to affected derived pages when applicable. To request a review, emailhello@hardwaterindex.com with the URL, disputed statement or value, and supporting source.