Capitol Water Corporation
EPA ID: ID4010022 · 9,000 people served · 33 ZIP codes
Capitol Water Corporation carries zero EPA violations in five years — a spotless record for a utility serving 9,000 residents.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Worsening · Risk tier: High · 95% chance of violation in next 12 months
Violations went from 2 (2023) to 66 (2025). The pattern suggests growing compliance challenges.
Service Area Map
Coverage area for Capitol Water Corporation Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Capitol Water Corporation serves a community with a median household income of $84,350 and an estimated 292,693 residents across its service area. Approximately 48% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
Capitol Water Corporation's water is pumped from underground aquifers. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
About 1% of homes in Ada County, Idaho rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Infrastructure Risk
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 14 detections recorded. 5 exceed federal EPA limits (4 ppt for PFOA/PFOS).
Comparable Water Systems
Similar-sized systems in Idaho
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
Capitol Water Corporation (EPA ID: ID4010022) is a community water system in Idaho that serves approximately 9,000 people from groundwater sources.
This system provides water to 33 ZIP codes across 2 communities.
Violation History
Lead & Copper
No Lead and Copper Rule sampling data available for this water system.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: 3 ZIP codes confirmed via EPA Community Water System Service Area Boundaries v3 plus 30 additional ZIPs inferred from SDWIS registry data. The EPA-confirmed set is the most reliable; SDWIS-inferred entries may be narrower than the real deployment area.
This system serves 33 ZIP codes:
83701 · 83702 · 83703 · 83704 · 83705 83706 · 83707 · 83708 · 83709 · 83711 83712 · 83713 · 83714 · 83715 · 83716 83717 · 83719 · 83720 · 83721 · 83722 83724 · 83725 · 83726 · 83727 · 83728 83729 · 83730 · 83731 · 83732 · 83735 83756 · 83757 · 83799
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Capitol Water Corporation (ID4010022) on EPA.gov.
Frequently Asked Questions
Is Capitol Water Corporation water safe to drink?
Based on EPA records, Capitol Water Corporation has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Capitol Water Corporation serve?
Capitol Water Corporation serves approximately 9,000 people across 33 ZIP codes in Idaho.
Where does Capitol Water Corporation get its water?
The primary water source is groundwater.
Federal UCMR5 PFAS Monitoring: Above Current MCL
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). One or more PFAS compounds were measured above the current state-enforceable MCL.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
How Water Systems Appear in Rankings
Water systems are evaluated by violation history, contaminant detections, and service population. Larger systems with more service connections appear in more rankings.