Arnold Water Hardness & Quality Report (2026)
Water Hardness
14.6 grains per gallon
Source
river
pH Level
8.5
neutral = 7.0
Lead
0.008 mg/L
✓ Below action level
TDS
620.2 mg/L
Est. Daily Cost
$0.67
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 Arnold, your appliances are currently losing 33% efficiency due to mineral buildup.
| Appliance | In Arnold | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 4.3 yrs | 12 yrs | -64% |
| Water Heater | 5.6 yrs | 15 yrs | -63% |
Regional Water Comparison
How Arnold compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Arnold, Missouri | 250.5 mg/L | 7.5 ppt | 🔴 Very Hard | river |
| Oakville, Missouri | 100 mg/L | 3.7 ppt | 🟡 Moderately Hard | river |
| Mehlville, Missouri | 222 mg/L | 6.8 ppt | 🔴 Very Hard | river |
| Concord, Missouri | 189 mg/L | 6 ppt | 🔴 Very Hard | river |
| Affton, Missouri | 204 mg/L | 6.3 ppt | 🔴 Very Hard | river |
National Benchmark
How Arnold compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Arnold | 250.5 mg/L | 🔴 High |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Arnold's Water Unique?
Local geology and source profile
Arnold, Missouri, in Jefferson County — a growing Jefferson County suburban community south of St. Louis at the Meramec River confluence with the Mississippi River corridor, known as part of the greater St. Louis Ozark foothills suburban expansion — receives its municipal water from Missouri American Water (MOAW) or the Arnold Water system, which draws from the Meramec River at Jefferson County intakes or from the Mississippi River through the St. Louis regional water distribution network.
The very hard 250.5 mg/L hardness and elevated TDS of 620.2 mg/L reflect the Meramec River's exceptional Ozark carbonate geology — the hardest river supply in the St. Louis area, significantly harder than the Mississippi River supply (which itself is already moderately hard). The Meramec River drains the heart of the Ozark Plateau — the most extensive carbonate karst landscape in North America west of the Appalachians — underlain by the Cambrian Gasconade Dolomite, Ordovician Roubidoux Formation (cherty dolomite), St. Peter Sandstone, and the overlying Cambrian Davis Formation carbonates. These ancient Ozark dolomites are characterized by enormous spring systems (the Meramec watershed contains some of Missouri's largest springs — Meramec Spring yields ~95 million gallons per day of hard dolomite spring water). This prolific dolomite spring baseflow dominates the Meramec River's hardness and TDS, producing extremely hard finished water when used as a municipal supply.
At 250.5 mg/L, Arnold's water is very hard. Scale builds rapidly in kettles and coffee machines within weeks, dishwashers require rinse aid or softener salt, and bathroom fixtures develop heavy calcium deposits. Monthly descaling of heating appliances is practical. A water softener is strongly recommended for Arnold homes. The PFAS level of 7.5 ppt warrants a certified drinking water filter — the Meramec River-Jefferson County corridor's industrial legacy, the St. Louis metropolitan area's chemical and manufacturing complex, and Mississippi River upstream PFAS sources contribute to the Arnold supply's PFAS background.
Geology & Source: Arnold in Jefferson County draws from Missouri American Water treating the Meramec River or Mississippi River — the Meramec River drains the Ozark Plateau (Cambrian and Ordovician Gasconade and Roubidoux dolostone), the most prolific dolomite spring system in Missouri — Ozark Cambrian-Ordovician dolomite spring baseflow from the Meramec watershed produces very hard water at 250.5 mg/L with elevated TDS 620 mg/L in this Jefferson County St. Louis suburb.