Tukwila Water Hardness & Quality Report (2026)
Water Hardness
2.7 grains per gallon
Source
reservoir
pH Level
7.4
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
95.7 mg/L
Est. Daily Cost
$0.12
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 Tukwila, your appliances are currently losing 6% efficiency due to mineral buildup.
| Appliance | In Tukwila | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 8.1 yrs | 8.5 yrs | -5% |
| Washing Machine | 11.9 yrs | 12 yrs | -1% |
| Water Heater | 13.8 yrs | 15 yrs | -8% |
Regional Water Comparison
How Tukwila compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Tukwila, Washington | 46 mg/L | 2.3 ppt | 🟢 Soft | reservoir |
| Bryn Mawr-Skyway, Washington | 29.5 mg/L | 1.8 ppt | 🟢 Soft | reservoir |
| SeaTac, Washington | 70.5 mg/L | 3.1 ppt | 🟡 Moderately Hard | reservoir |
| Renton, Washington | 27.5 mg/L | 1.7 ppt | 🟢 Soft | reservoir |
| Burien, Washington | 53.5 mg/L | 2.5 ppt | 🟢 Soft | reservoir |
National Benchmark
How Tukwila compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Tukwila | 46 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Tukwila's Water Unique?
Local geology and source profile
Tukwila, Washington, in King County — a King County city adjacent to SeaTac and Seattle, one of the most diverse cities in the United States (over 100 languages spoken), home of Westfield Southcenter shopping center and the Boeing Field / King County International Airport — receives its municipal water from Seattle Public Utilities (SPU) or the Tukwila Water Division, which draws from the Cedar River (Chester Morse Reservoir) or the South Fork Tolt River (Tolt Reservoir) — the same Cascade watershed sources serving the entire Seattle metropolitan system.
The very soft 46 mg/L hardness and very low TDS of 95.7 mg/L reflect the Cedar River watershed's Western Cascades volcanic character. The Cedar River drains the Cascade Range west of the Alpine Lakes Wilderness — terrain dominated by Tertiary basalt lava flows, andesite, and volcanic tuff. The Cedar River watershed is one of the most strictly protected municipal watersheds in North America — closed to public access and human activity — producing the consistently soft, high-quality water characteristic of the Seattle water supply system throughout King County.
At 46 mg/L, Tukwila's water is very soft — excellent for household use. Scale forms very slowly, soap lathers richly, and appliances maintain excellent efficiency. Annual descaling is more than sufficient. The PFAS level of 2.3 ppt is very good — reflecting the Cedar River watershed's protected pristine character and the limited direct PFAS sources in the Cascade headwaters.
Geology & Source: Tukwila in King County draws from the City of Seattle Public Utilities (SPU) or Tukwila Water on the Cedar River or South Fork Tolt River (Cedar-Chester Morse Reservoir) — the Cedar River drains the Cascades (Tertiary basalt and andesite) — Cascades volcanic basalt watershed drainage produces very soft water at 46 mg/L with very low TDS 96 mg/L in this King County Washington city.