Drinking Water — EPA SDWIS: Systems, Violations, Lead & Copper, PFAS (UCMR5)

Look up one US public water system by its PWSID (e.g. IL0970450). Returns the system's identity, type (community, transient, non-transient non-community), population served, service connections, owner and source type, the counties it serves, its current health-based violations (unresolved MCL, MRDL, and treatment-technique violations) from EPA SDWIS, plus its latest lead/copper 90th-percentile result and a summary of its UCMR5 PFAS sampling (whether sampled, analytes detected, maximum concentration). Use this when you already know the PWSID; if you only have a name or place, use search_water_systems first. This is the bundled overview — for the full monitoring-period lead/copper history use get_system_lead_copper, and for full per-analyte PFAS results use get_system_pfas. An unknown PWSID returns a no_data result, not an empty profile.

Search US public water systems by name, and optionally narrow by state (two-letter code), county name as reported to SDWIS (requires state), system type code (CWS, NTNCWS, TNCWS), or active systems only. Results are ordered by population served, largest first, and each result includes its count of current health-based violations. Returns brief records at most `limit` at a time (default 50, max 500) with no offset paging — narrow the filters to dig deeper. Use get_water_system with a result's PWSID for that system's full profile, violations, lead/copper and PFAS detail.

Summarize public water systems serving a US county: how many systems (and how many active), total population served, how many systems have current health-based violations and how many such violations are open, plus the worst-affected systems in the county. County names are as reported to SDWIS (uppercase). A county summary covers every system serving any part of the county; it is not a verdict on the water system at a specific address.

Summarize public water systems for a whole US state: how many systems (and how many active), total population served, how many systems have current health-based violations and how many such violations are open, the counties with the most affected systems, and the state's UCMR5 PFAS sampling coverage (systems sampled, systems with detections). Data is EPA SDWIS (2026 Q3 snapshot). Use get_county_water_summary instead for one county, and search_water_systems to find individual systems in the state.

List current (unresolved) health-based drinking water violations from EPA SDWIS: maximum contaminant level (MCL), maximum residual disinfectant level (MRDL), and treatment-technique violations whose status is Unaddressed or Addressed. Monitoring and reporting violations are excluded. Filter by state, by PWSID, or by contaminant code; most recent compliance periods first.

List every contaminant that has at least one current health-based violation in EPA SDWIS, with the number of open violations and the number of water systems affected, most violations first. Useful for seeing which contaminants drive current US drinking water violations.

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Lead and copper results for one water system by PWSID: the 90th percentile of tap samples for every reported Lead and Copper Rule monitoring period (latest first), with the lead action level (0.015 mg/L) and copper action level (1.3 mg/L) exceedance flags. The 90th percentile is a system-wide statistic, not a reading at any individual home's tap. Data is EPA SDWIS via ECHO. get_water_system shows only the latest period — use this tool for the full history and exceedance pattern. An unknown PWSID returns a no_data result.

PFAS results for one water system by PWSID from EPA's UCMR5 occurrence monitoring (2023-2025): whether the system was sampled, which of the 29 PFAS (plus lithium) were detected, detection counts, and maximum and mean detected concentrations in µg/L and ppt, with the 2024 PFAS MCLs shown as reference context. UCMR5 sampled only a subset of systems; no results means the system was not sampled under UCMR5, not that its water is PFAS-free. UCMR5 is occurrence monitoring, not compliance monitoring, so results are not compliance verdicts. Use this for one known system; use list_systems_with_pfas_detections instead to find or rank systems with detections across a state, county, or single analyte.

List water systems with at least one PFAS detection under EPA UCMR5 occurrence monitoring (2023-2025), worst first by maximum detected concentration. Filter by state, by county (requires state), or by a single analyte (e.g. PFOA, PFOS) to rank by that analyte's maximum. Only systems sampled under UCMR5 can appear; absence means not sampled, not PFAS-free.