Mount Vernon Water Hardness & Quality Report (2026)
Water Hardness
10.8 grains per gallon
Source
river
pH Level
8.1
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
377.8 mg/L
Est. Daily Cost
$0.49
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 Mount Vernon, your appliances are currently losing 25% efficiency due to mineral buildup.
| Appliance | In Mount Vernon | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 3.5 yrs | 8.5 yrs | -59% |
| Washing Machine | 6.8 yrs | 12 yrs | -43% |
| Water Heater | 8.2 yrs | 15 yrs | -45% |
Regional Water Comparison
How Mount Vernon compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Mount Vernon, Illinois | 184.5 mg/L | 6.5 ppt | 🔴 Very Hard | river |
| Centralia, Illinois | 238.5 mg/L | 8.3 ppt | 🔴 Very Hard | river |
| Herrin, Illinois | 223.5 mg/L | 7.8 ppt | 🔴 Very Hard | river |
| Marion, Illinois | 279.5 mg/L | 9.7 ppt | 🔴 Very Hard | river |
| Carbondale, Illinois | 210 mg/L | 7.4 ppt | 🔴 Very Hard | river |
National Benchmark
How Mount Vernon compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Mount Vernon | 184.5 mg/L | 🔴 High |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Mount Vernon's Water Unique?
Local geology and source profile
Mount Vernon, Illinois, in Jefferson County — the Jefferson County seat adjacent to Whittington and Woodlawn in south Illinois — receives its municipal water from the Mount Vernon Water Division, drawing from the Casey Fork Reservoir (Jefferson County) through the south Illinois water treatment system.
The hard 184.5 mg/L hardness and TDS of 377.8 mg/L reflect the south Illinois reservoir supply's moderate Pennsylvanian calcareous character — consistent with other south Illinois river communities (Carbondale: ~180 mg/L; Marion: ~188 mg/L). The Casey Fork at Jefferson County drains the Illinois Till Plain — Pennsylvanian McLeansboro Group (calcareous coal-measure shale — primary hardness contributor), calcareous Pleistocene Wisconsin Till (glacially ground Pennsylvanian carbonate — secondary contributor), and Mississippian Ste. Genevieve Limestone (calcareous — bedrock contribution). The Pennsylvanian calcareous shale produces the hard south Illinois supply.
At 184.5 mg/L, Mount Vernon's water is hard — scale builds steadily in kettles and appliances, dishwashers benefit from rinse aid, and water heaters should be descaled annually. Monthly descaling is recommended. The PFAS level of 6.5 ppt warrants a certified drinking water filter — the Jefferson County south Illinois industrial corridor and the Illinois PFAS background from the Scott Air Force Base complex (St. Clair County — AFFF) and regional industrial sources contribute to Mount Vernon's readings.
Geology & Source: Mount Vernon in Jefferson County draws from the Mount Vernon Water Division on the Casey Fork Reservoir (Jefferson County, south Illinois) — the Casey Fork drains the Illinois Till Plain (Pennsylvanian McLeansboro Group calcareous, calcareous glacial till) — Illinois Jefferson County Casey Fork Reservoir Pennsylvanian calcareous watershed produces hard water at 184.5 mg/L with TDS 377.8 mg/L.