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Local water dashboard

Official source aggregation

Water quality in Sonoma, CA 95476

A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for Sonoma County.

1 reported benchmark flag
Primary matched system
Sonoma, City Of
Source water
Groundwater
County
Sonoma County
Profile updated

At a glance

What the current records say

Hardness

Very Hard

180.5 PPM · 10.6 GPG

Compliance screen

No active flag

0 active health-based records

Lead 90th percentile

0 mg/L

0% of action level

Utility match

2 systems

Serves 11,725 people system-wide

Hardness meter

How hard is the water?

Very Hard

Estimated local hardness

USGS hardness classification scale

180.5 PPM

Soft
0–59Moderate
60–120Hard
121–180Very hard
181+

Parts per million

180.5

mg/L as CaCO₃ equivalent

Grains per gallon

10.6

1 GPG ≈ 17.1 PPM

What this means at home

At 180.5 PPM, mineral scale can build up on fixtures and heating elements, reduce soap lather, and leave visible spotting. Hardness is primarily an aesthetic and appliance concern—not itself a tap-water safety rating.

USGS sites used

226

Nearest site

1 mi

Observation range

Feb 8, 2016–Jul 31, 2023

Estimate confidence

Moderate

Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: 005N005W20M001M (Well).USGS source documentation ↗

Regional context

Is 95476 typical?

These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.

Sonoma median

181 PPM

About the same

1 indexed ZIP readings · Range 180.5–180.5 PPM

California median

189 PPM

8 PPM lower

678 indexed ZIP readings · Range 3.3–728.5 PPM

EPA benchmark screen

Contaminant snapshot

Available numerical results from associated SDWIS community water systems, compared with the applicable action level or federal MCL. Federal measured-value coverage is incomplete.

1 pass1 fail

Lead (PB90)

0 mg/L

Reported Dec 31, 2023

Copper (CU90)

1.5 mg/L

Reported Jan 31, 1993

Numerical coverage

2 comparable results

Missing values remain blank; absence is not treated as a pass.

Lead (90th percentile)

Measured in mg/L

Pass

Local 0

EPA limit 0.015

Local level is 0% of the listed EPA limit.

Copper (90th percentile)

Measured in mg/L

Fail

Local 1.5

EPA limit 1.3

Local level is 115% of the listed EPA limit.

Share of EPA benchmark

100% line = listed limit

EPA SDWIS compliance

Reported violation history

Open EPA source documentation ↗
2026Q2
All records
2
Health-based
0
Active health-based
0
Contaminant or ruleSystemStatusPeriod
LEAD AND COPPER RULE REVISIONSCA4910012UnaddressedJul 2, 2025
ArsenicCA4910012ResolvedApr 1, 2021through Jun 30, 2021

No reported violation does not prove that every contaminant was tested or absent; SDWIS measured values are incomplete and lag state records.

Solutions matcher

Your personalized water action plan

Matched to Sonoma ZIP 95476 using 180.5 PPM nearby hardness and 2 reported measurement benchmarks.

2 matches

Scale protection

High-Capacity Whole House Water Softener

180.5 PPM is 2× the high-hardness trigger used by this matcher.

Designed to reduce scale on fixtures, water heaters, glassware, and plumbing throughout the home.

Compare whole-house systems

Drinking water protection

Under-Sink Reverse Osmosis System

Copper (90th percentile) has a measured benchmark flag or active health-based SDWIS record in this profile.

A certified multi-stage RO system targets a broader range of dissolved contaminants at the kitchen tap.

Explore under-sink filtration

Affiliate disclosure: we may earn a commission from qualifying purchases, at no added cost to you. Product matching is educational and does not replace certified water testing.

Frequently asked

Water questions for Sonoma

Is tap water safe in Sonoma?+

EPA ECHO shows no active health-based violation for the associated systems in this reporting snapshot. This does not prove every contaminant is absent; federal records can lag and household plumbing can change tap conditions.

How hard is the water?+

Nearby USGS observations produce an estimate of 180.5 PPM, or 10.6 grains per gallon, classified as very hard. This is not a household tap measurement.

Do I need a water softener?+

At 180.5 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.