Stillwater Water Hardness & Quality Report (2026)
Water Hardness
~120–179 mg/L
Hardestimated · not lab-verified
Source
reservoir
pH Level
7.3
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
461 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 Stillwater, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Stillwater | 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 Stillwater compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Stillwater, Oklahoma | ≈ 120–179 mg/L | 64.7 ppt | 🟠 Hard | reservoir |
| Guthrie, Oklahoma | ≈ 180+ mg/L | 27.6 ppt | 🔴 Very Hard | reservoir |
| Ponca City, Oklahoma | 367.5 mg/L | 71.8 ppt | 🔴 Very Hard | reservoir |
| Edmond, Oklahoma | ≈ 120–179 mg/L | 93.1 ppt | 🟠 Hard | reservoir |
| Choctaw, Oklahoma | ≈ 120–179 mg/L | 0 ppt | 🟠 Hard | groundwater |
National Benchmark
How Stillwater compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Stillwater | ≈ 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 Stillwater's Water Unique?
Local geology and source profile
Stillwater Utilities Authority operates the Stillwater Water Treatment Plant at 1022 West Yost Road, sourcing raw water from Kaw Lake, approximately ten miles east of Ponca City in Kay County. The plant treats and distributes water to Stillwater citizens in Payne County, five rural water districts, and mobile home communities in Payne and Noble Counties. In 2017, it supplied over 2.3 billion gallons of safe drinking water. The 2025 Consumer Confidence Report covers 2024 data for Stillwater Water Plant OK1021220, confirming ongoing compliance with federal drinking water standards.
Kaw Lake's watershed lies within the Arkansas River basin, shaped by Permian bedrock including limestone, dolomite, and evaporites from the Blaine and Medicine Lodge formations that dissolve to impart minerals, yielding a hard supply. Surface runoff from surrounding farmlands and grasslands adds to the mineral load during high flows, while the reservoir moderates seasonal variations. No groundwater aquifer is involved; the geology favors higher dissolved solids typical of many Oklahoma reservoirs.
Hard water promotes limescale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. Boilers and fixtures show visible deposits, increasing energy costs. Regular vinegar descaling, installing sediment filters, and choosing scale-resistant appliances help mitigate effects. A water softener is recommended for households to prevent scaling and improve soap efficiency. The utility maintains EPA compliance using lime softening, ferric sulfate coagulation, and polymer aids; recent CCRs confirm no violations for lead, copper, or primary contaminants.
Geology & Source: Arkansas River basin reservoir — Permian limestone, dolomite, and evaporites from Blaine and Medicine Lodge formations; carbonate dissolution imparts hard character; agricultural runoff adds mineral load
Other Oklahoma Water Reports
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Frequently Asked Questions
Is Stillwater's water safe to drink?
Do I need a water softener in Stillwater?
How does Stillwater compare to the USA average?
Data Sources & Methodology
Water quality data for Stillwater 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.