Des Moines Water Hardness & Quality Report (2026)
Water Hardness
0.9 grains per gallon
Source
reservoir
pH Level
7.1
neutral = 7.0
Lead
0.001 mg/L
✓ Below action level
TDS
23.1 mg/L
Est. Daily Cost
$0.04
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 Des Moines, your appliances are currently losing 2% efficiency due to mineral buildup.
| Appliance | In Des Moines | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 9.1 yrs | 8.5 yrs | — |
| Washing Machine | 13 yrs | 12 yrs | — |
| Water Heater | 15 yrs | 15 yrs | — |
Regional Water Comparison
How Des Moines compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Des Moines, Washington | 15 mg/L | 1.3 ppt | 🟢 Soft | reservoir |
| SeaTac, Washington | 70.5 mg/L | 3.1 ppt | 🟡 Moderately Hard | reservoir |
| Burien, Washington | 53.5 mg/L | 2.5 ppt | 🟢 Soft | reservoir |
| Federal Way, Washington | 68.5 mg/L | 3 ppt | 🟡 Moderately Hard | reservoir |
| Lakeland North, Washington | 46.5 mg/L | 2.3 ppt | 🟢 Soft | reservoir |
National Benchmark
How Des Moines compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Des Moines | 15 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Des Moines's Water Unique?
Local geology and source profile
Des Moines, Washington, in King County — a major south Seattle suburban waterfront community (Des Moines is a significant King County city on the Puget Sound waterfront — one of the south Seattle shoreline communities along the Marine View Drive corridor; Des Moines has a significant waterfront marina (the Des Moines Marina is one of the major small boat marinas on the south Puget Sound) and views across Puget Sound to Vashon Island), a diverse King County community with a significant Hispanic-American, Asian-American (particularly Korean-American and Vietnamese-American), and working-class suburban population, adjacent to SeaTac (Seattle-Tacoma International Airport) and Burien in the south Seattle suburban corridor, home of the Des Moines Beach Park (a significant south King County waterfront park on the Puget Sound shoreline), and a community with a strong outdoor recreation and waterfront character — draws its municipal water supply via the Highline Water District (served by SPU). Water hardness in Des Moines measures 15 mg/L — classified as very soft.
Des Moines's very soft supply reflects the south Seattle SPU/Highline supply's calcareous-poor Cascade Mountains watershed. The Cedar River and Green River watersheds drain the Precambrian Cascade Mountain granite and metamorphic (calcareous-poor). The Highline Water District produces the very soft 15 mg/L.
With hardness at 15 mg/L, Des Moines residents enjoy very soft water. Highline Water District consistently delivers water meeting all Washington DOE and EPA Safe Drinking Water Act requirements.
Geology & Source: Surface supply from the Green River watershed (Tolt and Cedar River system) via the Seattle Public Utilities (SPU) or Highline Water District — the King County south Seattle suburban Des Moines corridor (Precambrian calcareous-poor Cascade Mountains granite — the extremely calcareous-poor south Seattle south King County supply; excellent softening); very soft supply at 15 mg/L in King County.