Water quality · Delaware
Water quality in Delaware
Water quality (EPA SDWIS) data for ZIP codes in Delaware. Pick a ZIP below to dive into the water quality summary.
Last verified 2026-05-13 · methodology
What lands here
Pages show the CWS serving the address, any health-based violations in the last 3 years, most recent lead and copper sampling result, and a link to the primary SDWIS record.
Source & refresh
EPA SDWIS. Refreshed quarterly (federal mandate). Primary source →
Delaware top concern
Sea-level rise, agricultural runoff
Delaware has the lowest mean elevation of any US state and FEMA NFHL coverage extends well inland in Sussex County. Agricultural runoff in poultry-heavy regions affects EPA SDWIS small-system nitrate readings. Lead-service-line inventories statewide are nearing 2024 LCRR baseline.
See Delaware state page for the full state-level rollup across all 12 dimensions.
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