Johnston Water Hardness & Quality Report (2026)
Water Hardness
19 grains per gallon
Source
river
pH Level
8.5
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
803 mg/L
Est. Daily Cost
$0.87
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 Johnston, your appliances are currently losing 43% efficiency due to mineral buildup.
| Appliance | In Johnston | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 3 yrs | 12 yrs | -75% |
| Water Heater | 5 yrs | 15 yrs | -67% |
Regional Water Comparison
How Johnston compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Johnston, Iowa | 324.5 mg/L | 6.7 ppt | 🔴 Very Hard | river |
| Urbandale, Iowa | 238 mg/L | 5 ppt | 🔴 Very Hard | river |
| Clive, Iowa | 290 mg/L | 6 ppt | 🔴 Very Hard | river |
| West Des Moines, Iowa | 133.5 mg/L | 2.9 ppt | 🟠 Hard | river |
| Ankeny, Iowa | 295 mg/L | 6.1 ppt | 🔴 Very Hard | river |
National Benchmark
How Johnston compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Johnston | 324.5 mg/L | 🔴 High |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Johnston's Water Unique?
Local geology and source profile
Johnston, Iowa, in Polk County — a fast-growing Polk County suburb north of Des Moines, home of Corteva Agriscience (formerly DuPont Pioneer — seed and agriculture company), a major northwestern Des Moines metro residential community — receives its municipal water from the Des Moines Water Works (DMWW), which draws from the Des Moines River and the Raccoon River through the Greater Des Moines metropolitan water supply system. The DMWW serves Johnston and all communities in the Des Moines metro area.
The extremely hard 324.5 mg/L hardness and very high TDS of 803 mg/L reflect the Raccoon River-Des Moines watershed's extremely carbonate-rich central Iowa geology. The Raccoon River and Des Moines River drain the Central Iowa Till Plain — one of the most recently glaciated landscapes in North America (Wisconsin Glaciation, ending ~12,000 years ago), underlain by the Iowa-Des Moines Lobe glacial till (extremely rich in calcareous limestone and dolomite fragments from the Silurian, Devonian, and Mississippian carbonate formations of Iowa). The Iowa Des Moines Lobe deposits some of the thickest and most calcareous glacial tills in the Midwest, producing extremely hard surface water through continuous dissolution of fresh glacial carbonate. Des Moines Water Works is famous for its nitrate removal operations (the Raccoon River has among the highest agricultural nitrate loads in the US), but the supply is also exceptionally hard.
At 324.5 mg/L with TDS 803 mg/L, Johnston residents face extremely hard water. Scale forms almost immediately on appliances and fixtures. A whole-house water softener is essential. The PFAS level of 6.7 ppt warrants a certified drinking water filter — the Raccoon River watershed's intensive corn/soy agriculture (Corteva/Pioneer seed corn operations), the Iowa Army Ammunition Plant (Middletown, Iowa — AFFF user), and the Des Moines metro industrial complex contribute to Johnston's PFAS reading.
Geology & Source: Johnston in Polk County draws from the Des Moines Water Works treating the Des Moines River and Raccoon River — the Raccoon River drains the Central Iowa Till Plain (Pleistocene glacial till over Pennsylvanian limestone and shale cyclothem sequence) and the Iowa-Des Moines Lobe glaciated terrain — Pennsylvanian carbonate and glacial till drainage produces extremely hard water at 324.5 mg/L with very high TDS 803 mg/L in this Polk County Iowa suburb.