Centennial Water Hardness & Quality Report (2026)
Water Hardness
5.9 grains per gallon
Source
reservoir
pH Level
7.7
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
204.8 mg/L
Est. Daily Cost
$0.27
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 Centennial, your appliances are currently losing 14% efficiency due to mineral buildup.
| Appliance | In Centennial | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6.3 yrs | 8.5 yrs | -26% |
| Washing Machine | 9.8 yrs | 12 yrs | -18% |
| Water Heater | 11.5 yrs | 15 yrs | -23% |
Regional Water Comparison
How Centennial compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Centennial, Colorado | 101.5 mg/L | 3.7 ppt | 🟡 Moderately Hard | reservoir |
| Castlewood, Colorado | 93 mg/L | 3.4 ppt | 🟡 Moderately Hard | reservoir |
| Lone Tree, Colorado | 91 mg/L | 3.3 ppt | 🟡 Moderately Hard | reservoir |
| Southglenn, Colorado | 100.5 mg/L | 3.6 ppt | 🟡 Moderately Hard | reservoir |
| Greenwood Village, Colorado | 84.5 mg/L | 3.1 ppt | 🟡 Moderately Hard | reservoir |
National Benchmark
How Centennial compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Centennial | 101.5 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Centennial's Water Unique?
Local geology and source profile
Centennial, Colorado — a major southern Denver suburb in Arapahoe County — receives its municipal water supply through the Arapahoe County Water and Wastewater Authority (ACWWA) and South Arapahoe Metropolitan District, sourcing from Denver Water treated South Platte headwater system water and supplemental groundwater from the Denver Basin aquifer system (Arapahoe and Laramie-Fox Hills aquifers) in Arapahoe County. The Denver Basin is a non-renewable bedrock aquifer underlying the eastern Denver metropolitan area. Water hardness measures 101.5 mg/L — classified as moderately hard.
Centennial's moderate hardness reflects the blended supply of soft Denver Water surface water with Denver Basin groundwater. The South Platte headwater component drains the Front Range Precambrian crystalline terrain (Pikes Peak Granite batholith, Idaho Springs Formation gneiss) — very soft source water. However, the Denver Basin Arapahoe aquifer groundwater — drawn from Late Cretaceous Arapahoe Formation sandstone and associated calcareous cement — contributes moderate dissolved calcium and bicarbonate to the supply blend. Denver Basin groundwater has longer subsurface residence times in calcareous Cretaceous marine sandstone, accumulating moderate mineral content before pumping.
At 101.5 mg/L, Centennial residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. Dishwashers produce cleaner glassware with rinse-aid, and water heaters benefit from annual inspection for element scale. ACWWA and Denver Water consistently deliver water meeting all Colorado CDPHE and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from South Platte River headwaters via Denver Water regional distribution and the Arapahoe County Water and Wastewater Authority (ACWWA) — the South Platte headwater Front Range Precambrian granite and metamorphic terrain produces soft base water; limited Denver Basin aquifer (Arapahoe Formation) groundwater fraction adds moderate hardness producing supply at 101.5 mg/L in southeast Arapahoe County.