Decatur Water Hardness & Quality Report (2026)
Water Hardness
8.6 grains per gallon
Source
river
pH Level
7.9
neutral = 7.0
Lead
0.003 mg/L
✓ Below action level
TDS
265.8 mg/L
Est. Daily Cost
$0.39
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 Decatur, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Decatur | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4.7 yrs | 8.5 yrs | -45% |
| Washing Machine | 8.2 yrs | 12 yrs | -32% |
| Water Heater | 9.7 yrs | 15 yrs | -35% |
Regional Water Comparison
How Decatur compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Decatur, Illinois | 147 mg/L | 5.2 ppt | 🟠 Hard | river |
| Lincoln, Illinois | 132.5 mg/L | 4.7 ppt | 🟠 Hard | river |
| Bloomington, Illinois | 191.5 mg/L | 6.7 ppt | 🔴 Very Hard | river |
| Normal, Illinois | 231 mg/L | 8.1 ppt | 🔴 Very Hard | river |
| Mattoon, Illinois | 109 mg/L | 3.9 ppt | 🟡 Moderately Hard | river |
National Benchmark
How Decatur compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Decatur | 147 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Decatur's Water Unique?
Local geology and source profile
Decatur, Illinois, the Macon County seat in central Illinois — a major Archer Daniels Midland (ADM) agribusiness hub and soybean processing center — draws its municipal water supply from Lake Decatur (an impoundment on the Sangamon River within the Decatur city limits) via the City of Decatur Water Management Division, treating Sangamon River water at the Scott Park Water Treatment Plant. Lake Decatur is subject to ongoing algae and nutrient challenges from the agricultural Sangamon River watershed. Water hardness in Decatur measures 147 mg/L — classified as moderately hard.
Decatur's moderate hardness reflects the Sangamon River watershed's central Illinois geology. The Sangamon River drains the Macon County–Sangamon County glacial plain — thick Quaternary Wisconsin glacial till derived from grinding the Mississippian Salem Limestone, Aux Vases Sandstone, and Devonian Grand Tower Formation (limestone) of the Illinois Basin. The calcareous glacial till throughout the Sangamon River watershed leaches dissolved calcium and bicarbonate into the river and Lake Decatur. Additionally, the Sangamon River passes over exposed Devonian Lingle Formation limestone near Decatur, adding direct carbonate dissolution. The combination of calcareous till leachate and carbonate bedrock contact produces the 147 mg/L moderately hard supply.
At 147 mg/L, Decatur residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. City of Decatur Water Management Division consistently delivers water meeting all Illinois EPA and federal EPA Safe Drinking Water Act requirements.
Geology & Source: Reservoir supply from Lake Decatur (Sangamon River) via the City of Decatur Water Management Division — the Sangamon River Central Illinois watershed draining the Mississippian Salem and Aux Vases Limestone, Devonian Grand Tower Formation, and Quaternary calcareous glacial till of Macon County; moderately hard supply at 147 mg/L in Macon County.