Duncan Water Hardness & Quality Report (2026)
Water Hardness
~120–179 mg/L
Hardestimated · not lab-verified
Source
reservoir
pH Level
8.5
neutral = 7.0
Lead
0.009 mg/L
✓ Below action level
TDS
973.1 mg/L
Est. Daily Cost
$0.40
energy & soap waste
Source: See methodology section below · 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 Duncan, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Duncan | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6.8 yrs | 8.5 yrs | -20% |
| Washing Machine | 9.6 yrs | 12 yrs | -20% |
| Water Heater | 12 yrs | 15 yrs | -20% |
Regional Water Comparison
How Duncan compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Duncan, Oklahoma | ≈ 120–179 mg/L | 77.1 ppt | 🟠 Hard | reservoir |
| Lawton, Oklahoma | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | reservoir |
| Chickasha, Oklahoma | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | reservoir |
| Burkburnett, Texas | ≈ 120–179 mg/L | 26.4 ppt | 🟠 Hard | reservoir |
| Wichita Falls, Texas | ≈ 120–179 mg/L | 161 ppt | 🟠 Hard | reservoir |
National Benchmark
How Duncan compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Duncan | ≈ 120–179 mg/L | 🟠 Moderate |
| USA National Avg | 151 mg/L | 🟠 Moderate |
| Scarsdale Top Rated | 0.02 mg/L | 🟢 None |
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What Makes Duncan's Water Unique?
Local geology and source profile
The Duncan Public Utilities Authority manages the municipal water supply for Duncan, Oklahoma, serving the city and surrounding areas in Stephens County. The system draws from reservoir sources — Lake Duncan and Fuqua Lake — on the Washita River watershed in south-central Oklahoma. While specific treatment plant names and full operational details were not available in retrieved sources, an official Consumer Confidence Report (CCR) exists for the system under EPA SDWIS ID OK1010809, covering 2024 data and documenting the utility's compliance monitoring, treatment methods, and contaminant testing results.
The Washita River drains south-central Oklahoma's Permian Anadarko Basin, cutting across Permian Red Bed evaporites — including gypsum and anhydrite — along with the calcareous Wellington Formation and Blaine Formation gypsite. Intense dissolution of these evaporite and carbonate rock layers releases large quantities of calcium, magnesium, and sulfate into the water, producing extreme hardness with near-1,000 TDS characteristic of this basin.
At extreme hardness levels, scale buildup in pipes, water heaters, dishwashers, and washing machines is aggressive and can significantly reduce appliance efficiency and lifespan. Mineral deposits form rapidly on fixtures, faucet aerators, and heating elements. A water softener is strongly recommended for virtually all households to protect plumbing infrastructure and appliances. Regular descaling of kettles and appliances is essential. The official CCR available through the City of Duncan or EPA SDWIS database provides detailed compliance data for lead, copper, and other regulated contaminants.
Geology & Source: Washita River watershed, Stephens County — Permian Anadarko Basin; Permian Red Bed evaporites (gypsum, anhydrite), Wellington Formation, Blaine Formation gypsite — intense evaporite and carbonate dissolution produces extreme hardness
Other Oklahoma Water Reports
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Frequently Asked Questions
Is Duncan's water safe to drink?
Do I need a water softener in Duncan?
How does Duncan compare to the USA average?
Data Sources & Methodology
Water quality data for Duncan is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.
Water Hardness
Modelled estimate based on state-level USGS geological survey data for this region. No direct USGS Water Quality Portal measurement was matched to this city — the value reflects a statistical range calibrated to the state's dominant rock types and typical source water characteristics.
pH
Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.
TDS — Total Dissolved Solids
Estimated using a derived ratio from water hardness and regional conductance profiles. TDS in natural water correlates strongly with total mineral content including hardness ions.
PFAS — Perfluoroalkyl and Polyfluoroalkyl Substances
EPA UCMR5 (5th Unregulated Contaminant Monitoring Rule, 2023–2025) — sum of PFAS compounds detected at the public water system serving this city. A value of 0 indicates the system was sampled with no detection above reporting limits.
Lead
Modelled estimate based on the EPA Lead and Copper Rule 90th-percentile tap-sample methodology. No publicly available per-city lead dataset with sufficient national coverage exists. Values are a conservative baseline derived from city population tier and infrastructure age — all estimates are maintained below the EPA action level of 0.015 mg/L.
Appliance Lifespan
Calculated from water hardness using a linear degradation model. Baseline lifespans represent soft-water performance (kettle: 8.5 yrs, washing machine: 12.0 yrs, water heater: 15.0 yrs). Hard water mineral scale progressively reduces operational life in direct proportion to hardness concentration.