DIAMOND A MUTUAL WATER COMPANY

SONOMA, CA · ~640 people served

Check your exact address → SONOMA overview

Excellent

PurityRadar safety score

PWSID

CA4900562

State

California

City

SONOMA

Population served

640

Primary source

Groundwater

Score history

No change since tracking began Jun 18, 2026.

Jun 18, 2026 · score 85 Jun 18, 2026 · score 85

2 score updates logged since tracking began Jun 18, 2026. Each future EPA re-score adds a point.

PFAS & contaminant readings

No PFAS detections are on record for this system from EPA’s UCMR5 monitoring (2023–25). Absence of a detection isn’t a guarantee — not every system was sampled, and this dataset doesn’t cover other contaminants.

Violations & enforcement

Violations on record

Unaddressed

Health-based

Enforcement actions

From EPA ECHO (SDWIS), most recent enforcement Oct 2014. Official EPA record →

Reporting · EPA contaminant 5200 began Oct 2024 Unaddressed

Treatment technique · EPA contaminant 5200 health-based began Oct 2024 Unaddressed

Max contaminant level (MCL) · Total coliform health-based began Sep 2014 Resolved

Monitoring & reporting · Nitrate began Jan 2006 Resolved

Monitoring & reporting · Total coliform began Aug 2002 Resolved

Monitoring & reporting · Total coliform began Oct 1998 Resolved

Monitoring & reporting · Total coliform began Sep 1998 Resolved

Recent enforcement actions

State action · SOX Oct 2014
State action · SFL Oct 2014
State action · SFL Jun 2007
State action · SOX Jun 2007
State action · SOX Sep 2002
State action · SFL Sep 2002
State action · SOX Dec 1998
State action · SFL Nov 1998

This profile is built from EPA public records for system CA4900562 — SDWIS violations and UCMR5 PFAS sampling. The score is system-level and can’t account for your home’s plumbing (older pipes can add lead at the tap). For health decisions, check your exact address, read the utility’s Consumer Confidence Report, and confirm with your provider.