West Lake Sammamish Water Hardness & Quality Report (2026)
Water Hardness
1 grains per gallon
Source
reservoir
pH Level
7.1
neutral = 7.0
Lead
0.002 mg/L
✓ Below action level
TDS
27.6 mg/L
Est. Daily Cost
$0.05
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
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 West Lake Sammamish, your appliances are currently losing 2% efficiency due to mineral buildup.
| Appliance | In West Lake Sammamish | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 9 yrs | 8.5 yrs | — |
| Washing Machine | 13 yrs | 12 yrs | — |
| Water Heater | 14.9 yrs | 15 yrs | -1% |
Regional Water Comparison
How West Lake Sammamish compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ West Lake Sammamish, Washington | 17.5 mg/L | 1.4 ppt | 🟢 Soft | reservoir |
| Sammamish, Washington | 60 mg/L | 2.7 ppt | 🟡 Moderately Hard | reservoir |
| City of Sammamish, Washington | 59.5 mg/L | 2.7 ppt | 🟢 Soft | reservoir |
| Issaquah, Washington | 44 mg/L | 2.2 ppt | 🟢 Soft | reservoir |
| Redmond, Washington | 24.5 mg/L | 1.6 ppt | 🟢 Soft | reservoir |
National Benchmark
How West Lake Sammamish compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ West Lake Sammamish | 17.5 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes West Lake Sammamish's Water Unique?
Local geology and source profile
West Lake Sammamish, Washington, an unincorporated community in King County — a major east King County community on Lake Sammamish (West Lake Sammamish is on the western shore of Lake Sammamish — a large natural lake east of Lake Washington in King County, one of the premier residential lakefront areas in the Seattle metro), adjacent to Redmond and Bellevue in the east King County technology corridor (the West Lake Sammamish area is surrounded by Microsoft, Google, Meta, and numerous technology company campuses in the Redmond–Bellevue tech hub), a diverse King County community with a significant Indian-American and Chinese-American technology professional population, and an affluent east King County lakefront residential community — draws its municipal water supply via the Seattle Public Utilities. Water hardness in West Lake Sammamish measures 17.5 mg/L — classified as extremely soft.
West Lake Sammamish's extremely soft supply reflects the Seattle Public Utilities Cedar River watershed's highly calcareous-poor Cascade geology. The Cedar River (Chester Morse Lake) at West Lake Sammamish–King County drains: the Western Cascades calcareous-poor volcanic and metamorphic terrain (the highly calcareous-poor Cascade volcanic basalt, andesite, and metamorphic rocks — virtually no dissolved calcium carbonate); and the Quaternary calcareous-poor Cascade glacial outwash (calcareous-poor granite and volcanic mineral content). The calcareous-poor Cedar River watershed produces the extremely soft 17.5 mg/L.
With hardness at 17.5 mg/L, West Lake Sammamish residents enjoy extremely soft water. Seattle Public Utilities consistently delivers water meeting all Washington State DOE and EPA Safe Drinking Water Act requirements.
Geology & Source: Mountain reservoir supply from the Cedar River (Chester Morse Lake watershed) via the Seattle Public Utilities (SPU) — the King County east suburban Seattle Lake Sammamish corridor (Quaternary calcareous-poor Cascade volcanic glacial outwash and Eocene calcareous-poor Puget Group sediment — the highly calcareous-poor east King County Cascade supply; Seattle Public Utilities east distribution to West Lake Sammamish zone); extremely soft supply at 17.5 mg/L in King County.