Mariani Water System Inc.
EPA ID: WA5351675 · 138 people served · 1 ZIP code
Mariani Water System Inc. earns a clean bill from EPA monitoring — no violations in five years across a service area of 138 people.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for Mariani Water System Inc. Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Mariani Water System Inc. serves a community with a median household income of $148,692 and an estimated 6,351 residents across its service area.
💧 Where Does Your Water Come From?
Mariani Water System Inc.'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 2% of homes in King County, Washington rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 70th percentile nationally for proximity to Superfund (NPL) sites. Groundwater sources near contaminated sites may face elevated risk from industrial chemicals.
Infrastructure Risk
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 5 detections recorded. 1 exceeds federal EPA limits (4 ppt for PFOA/PFOS).
Comparable Water Systems
Similar-sized systems in Washington
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
Mariani Water System Inc. (EPA ID: WA5351675) is a community water system in Washington that serves approximately 138 people from groundwater sources.
This system serves ZIP code 98010 in Black Diamond.
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
- 98010 — Black Diamond
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Mariani Water System Inc. (WA5351675) on EPA.gov.
Frequently Asked Questions
Is Mariani Water System Inc. water safe to drink?
Based on EPA records, Mariani Water System Inc. has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Mariani Water System Inc. serve?
Mariani Water System Inc. serves approximately 138 people across 1 ZIP code in Washington.
Where does Mariani Water System Inc. get its water?
The primary water source is groundwater.