Sonoma County Mutual Water Company
EPA ID: CA4900640 · 40 people served · 60 ZIP codes
EPA data: Sonoma County Mutual Water Company — zero violations, five years, 40 served.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Stable · Risk tier: High · 85% chance of violation in next 12 months
Violations went from 60 (2021) to 120 (2024). Violation counts have remained relatively steady.
Service Area Map
Coverage area for Sonoma County Mutual Water Company Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Sonoma County Mutual Water Company serves a community with a median household income of $145,717 and an estimated 836,321 residents across its service area. Approximately 79% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
Environmental Justice Note: 33% of the population in this service area is classified as disadvantaged under EPA's EJScreen criteria. Communities with higher disadvantaged populations often face disproportionate environmental and health burdens, including aging water infrastructure and limited resources for remediation.
🌊 Where Does Your Water Come From?
Sonoma County Mutual Water Company's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 5% of homes in San Francisco County, California 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.
Infrastructure Risk
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 7 detections recorded.
Comparable Water Systems
Similar-sized systems in California
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
Sonoma County Mutual Water Company (EPA ID: CA4900640) is a community water system in California that serves approximately 40 people from surface water sources.
This system provides water to 60 ZIP codes across 1 community.
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
This system serves 60 ZIP codes:
94101 · 94102 · 94103 · 94104 · 94105 94107 · 94108 · 94109 · 94110 · 94111 94112 · 94114 · 94115 · 94116 · 94117 94118 · 94119 · 94120 · 94121 · 94122 94123 · 94124 · 94125 · 94126 · 94127 94128 · 94129 · 94130 · 94131 · 94132 94133 · 94134 · 94136 · 94137 · 94139 94140 · 94141 · 94142 · 94143 · 94144 94145 · 94146 · 94147 · 94150 · 94151 94153 · 94154 · 94156 · 94158 · 94159 94160 · 94161 · 94162 · 94163 · 94164 94171 · 94172 · 94175 · 94177 · 94188
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Sonoma County Mutual Water Company (CA4900640) on EPA.gov.
Frequently Asked Questions
Is Sonoma County Mutual Water Company water safe to drink?
Based on EPA records, Sonoma County Mutual Water Company has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Sonoma County Mutual Water Company serve?
Sonoma County Mutual Water Company serves approximately 40 people across 60 ZIP codes in California.
Where does Sonoma County Mutual Water Company get its water?
The primary water source is surface water.
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
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.