How does Newcastle's water compare to the national average?

The USA national average is 150 mg/L. Newcastle at 71.5 mg/L is 79 mg/L softer than average.

Newcastle Water Hardness & Quality Report (2026)

Water Hardness

71.5mg/L

Moderately Hard

4.2 grains per gallon

Source

reservoir

pH Level

7.7

neutral = 7.0

Lead

0.008 mg/L

✓ Below action level

TDS

180.5 mg/L

Est. Daily Cost

$0.19

energy & soap waste

Source: USGS Water Quality Portal · Updated 2026

71.5mg/L as CaCO₃Moderately Hard

0–60

mg/L

Soft

61–120

mg/L

Moderately Hard

121–180

mg/L

Hard

180+

mg/L

Very Hard

Appliance Damage Report

In Newcastle, your appliances are currently losing 10% efficiency due to mineral buildup.

Appliance	In Newcastle	Soft Water City	Efficiency Loss
Kettle	7.2 yrs	8.5 yrs	-15%
Washing Machine	11 yrs	12 yrs	-8%
Water Heater	12.7 yrs	15 yrs	-15%

Regional Water Comparison

How Newcastle compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Newcastle, Washington	71.5 mg/L	3.1 ppt	🟡 Moderately Hard	reservoir
West Lake Sammamish, Washington	17.5 mg/L	1.4 ppt	🟢 Soft	reservoir
East Renton Highlands, Washington	42 mg/L	2.2 ppt	🟢 Soft	reservoir
Mercer Island, Washington	30.5 mg/L	1.8 ppt	🟢 Soft	reservoir
Renton, Washington	27.5 mg/L	1.7 ppt	🟢 Soft	reservoir

National Benchmark

How Newcastle compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ Newcastle	71.5 mg/L	🟡 Low
USA National Avg	150 mg/L	🟠 Moderate
Badger Top Rated	8.5 mg/L	🟢 None

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What Makes Newcastle's Water Unique?

Local geology and source profile

Source: ReservoirTDS: 180.5 mg/LpH: 7.7

Newcastle, Washington, in King County — a King County city adjacent to Renton and Bellevue in the southeast King County lake district — receives its water from Seattle Public Utilities or Cascade Water Alliance, drawing from the Cedar River watershed through the west-central Washington distribution.

The soft 71.5 mg/L hardness and TDS of 180.5 mg/L reflect the King County Cedar River supply's soft Cascade volcanic character — the Quaternary Cascade andesite and Precambrian Belt Supergroup are both highly insoluble formations contributing negligible dissolved minerals to the pristine Cedar River watershed in the King County Cascade foothills (compare Renton WA: 69/174 in King County comparable; Bellevue WA: 73/186 in King County comparable; Newcastle consistent soft from the same King County Cedar River Cascade volcanic supply). The Cedar River watershed — Quaternary Cascade andesite (insoluble — primary dilutant), Precambrian Belt Supergroup (slightly insoluble — secondary dilutant), and Quaternary glacial outwash (slightly calcareous — minor TDS).

At 71.5 mg/L with TDS 181, Newcastle's water is soft — minimal scale buildup. Annual descaling is appropriate. The PFAS level of 3.1 ppt is low — a clean result for King County. Review Seattle Public Utilities' annual water quality report.

Geology & Source: Newcastle in King County draws from the Seattle Public Utilities on the Cedar River watershed (King County, west-central Washington) — the Cedar River watershed drains Quaternary Cascade andesite (insoluble) and Precambrian Belt Supergroup (slightly insoluble) — Washington King County Cedar River Cascade volcanic supply produces soft water at 71.5 mg/L with TDS 180.5 mg/L.

Other Washington Water Reports

West Lake Sammamish

17.5 mg/L

🟢 Soft

East Renton Highlands

42 mg/L

🟢 Soft

Mercer Island

30.5 mg/L

🟢 Soft

Renton

27.5 mg/L

🟢 Soft

Frequently Asked Questions

Is Newcastle's water safe to drink?

Yes. Newcastle's water meets all federal safety standards. The hardness is 71.5 mg/L (Moderately Hard), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in Newcastle?

Newcastle's water is moderately hard at 71.5 mg/L. A water softener is generally not necessary, though a carbon filter can improve taste and remove any remaining chlorine.

How does Newcastle compare to the USA average?

The USA national average is 150 mg/L. Newcastle at 71.5 mg/L is 79 mg/L below the national average. The softest major city is Badger at just 8.5 mg/L.