Lake Saint Louis Water Hardness & Quality Report (2026)
Water Hardness
7.9 grains per gallon
Source
river
pH Level
7.8
neutral = 7.0
Lead
0.003 mg/L
✓ Below action level
TDS
243.7 mg/L
Est. Daily Cost
$0.36
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 Lake Saint Louis, your appliances are currently losing 18% efficiency due to mineral buildup.
| Appliance | In Lake Saint Louis | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.2 yrs | 8.5 yrs | -39% |
| Washing Machine | 8.6 yrs | 12 yrs | -28% |
| Water Heater | 10.2 yrs | 15 yrs | -32% |
Regional Water Comparison
How Lake Saint Louis compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Lake Saint Louis, Missouri | 134.5 mg/L | 4.6 ppt | 🟠 Hard | river |
| Dardenne Prairie, Missouri | 289.5 mg/L | 8.5 ppt | 🔴 Very Hard | river |
| Wentzville, Missouri | 267.5 mg/L | 8 ppt | 🔴 Very Hard | river |
| O'Fallon, Missouri | 279 mg/L | 8.3 ppt | 🔴 Very Hard | river |
| Saint Peters, Missouri | 137 mg/L | 4.6 ppt | 🟠 Hard | river |
National Benchmark
How Lake Saint Louis compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Lake Saint Louis | 134.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Lake Saint Louis's Water Unique?
Local geology and source profile
Lake Saint Louis, Missouri, in Saint Charles County — a Saint Charles County city adjacent to O'Fallon and Wentzville in the west St. Louis metro — receives its water from Missouri American Water, drawing from the Missouri River (Saint Charles County) through the west St. Louis metro distribution.
The moderately hard 134.5 mg/L hardness and TDS of 243.7 mg/L are softer than the St. Louis metro east Missouri American Water communities (Jennings: 193 mg/L; Ferguson: ~195 mg/L) — reflecting the west Saint Charles County position where the Missouri River supply is treated at a different intake or blend ratio producing a softer supply character. The Missouri River at Saint Charles County drains the same Ozark Plateau calcareous formations — Ordovician Gasconade Dolomite (dolomite — TDS contributor), Mississippian Ste. Genevieve Limestone (calcareous — primary hardness contributor), and Cambrian Gasconade Formation (calcareous).
At 134.5 mg/L, Lake Saint Louis' water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 4.6 ppt warrants a certified drinking water filter — Whiteman Air Force Base (Johnson County — AFFF) and the west St. Louis metro industrial corridor contribute to Lake Saint Louis' readings.
Geology & Source: Lake Saint Louis in Saint Charles County draws from the Missouri American Water on the Missouri River (Saint Charles County, east-central Missouri) — the Missouri River at St. Charles County drains the Ozark Plateau (Ordovician Gasconade Dolomite, Mississippian Ste. Genevieve Limestone) — Missouri Saint Charles County Missouri River Ozark calcareous-dolomitic watershed produces moderately hard water at 134.5 mg/L with TDS 243.7 mg/L.