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City water profile

Black Diamond water quality

Compare local ZIP estimates, evidence quality, associated public systems, and compliance history for Black Diamond, Washington.

Median indexed hardness

104PPM

One indexed ZIP

Range 103.5–103.5 PPM

State comparison
At state median
State hardness rank
#74 of 133
Matched utilities
1
Active health records
0

City summary

What the indexed records say

Black Diamond has 1 published ZIP profile across King County. The indexed median is 104 PPM, compared with 104 PPM across Washington.

Among the 133 Washingtoncities with an indexed median, Black Diamond ranks #74from highest to lowest. Across all 189 state ZIP profiles, available estimates run from 20.6to 238 PPM.

Because only one ZIP is represented, the city median and range are the same local estimate. It should not be read as multiple independent samples across the community.

Hardness distribution

How local ZIP estimates compare

Soft0 ZIPs
Moderately hard1 ZIP
Hard0 ZIPs
Very hard0 ZIPs

1 of 1 ZIP profiles have a hardness estimate. Bars count ZIP profiles, not households or laboratory samples.

Evidence quality

Distance, dates, and confidence

Median nearest distance
2.9 miles
Profiles with evidence
1/1

Confidence labels

High: 0Moderate: 1Low: 0

Observation window: Jun 29, 2016 to Aug 12, 2024.

ZIP directory

Water reports in Black Diamond

Open a ZIP for site-level provenance and measurements.

ZIP code

98010

Moderately Hard

103.5 PPM

Nearest site
2.9 mi
Confidence
Moderate

View full ZIP evidence →

Public water systems

Utilities associated with this city

Black Diamond Water Dept

PWSID WA5307220

Groundwater
System population served
6,407
Last reported
Jun 19, 2026

A municipal system, in-state city, and served county all agree with this Census ZCTA.

Compliance history

What EPA records show

No active health-based violation appears among the associated systems in the represented EPA reporting quarter. This does not mean every contaminant was tested at every tap.

No violation records are included in the current lookback window.

Practical next steps

Move from index to evidence

  1. 1. Open your ZIP. Check distance, dates, confidence, and the associated utility.
  2. 2. Read the current CCR. Confirm source water, detections, limits, ranges, and notices.
  3. 3. Test the tap when needed. Confirm health concerns or treatment sizing with the right method.

Questions people ask

About water in Black Diamond

Is the water hard?

The indexed city median is 104 PPM. Open the ZIP report to verify the distance and confidence behind that estimate.

Is the tap water safe?

Compliance history is utility-wide and cannot guarantee conditions at every tap. Check current notices and test when address-specific evidence is needed.

Do I need treatment?

Choose treatment only after confirming the problem at the property. A softener targets hardness; contaminant treatment requires a matching, verified performance claim.