Key West Water Hardness & Quality Report (2026)
Water Hardness
~120–179 mg/L
Hardestimated · not lab-verified
Source
groundwater
pH Level
8.5
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
843.6 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 Key West, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Key West | 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 Key West compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Key West, Florida | ≈ 120–179 mg/L | 187.5 ppt | 🟠 Hard | groundwater |
| Marco Island, Florida | ≈ 120–179 mg/L | 46.5 ppt | 🟠 Hard | reservoir |
| Marco, Florida | ≈ 180+ mg/L | 46.5 ppt | 🔴 Very Hard | reservoir |
| Key Largo, Florida | ≈ 180+ mg/L | 11 ppt | 🔴 Very Hard | groundwater |
| Florida City, Florida | ≈ 120–179 mg/L | 52.8 ppt | 🟠 Hard | groundwater |
National Benchmark
How Key West compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Key West | ≈ 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 Key West's Water Unique?
Local geology and source profile
The Florida Keys Aqueduct Authority (FKAA) is the primary water utility serving Key West and the Florida Keys, including Monroe County. FKAA sources all its water from the Floridan Aquifer, transporting treated groundwater via a 40-mile pipeline — the Floridan Aqueduct — to Key West. Treatment occurs at the FKAA's John A. Chinnis Jr. Water Treatment Plant in Florida City, with distribution spanning the island chain from Key Largo to Key West, providing potable water to over 100,000 residents and visitors throughout the service area.
The water supply originates within the Lower Florida Keys watershed, part of the broader South Florida hydrologic region (HUC 03090203). Water is pumped from wells penetrating the Floridan Aquifer System, where it interacts with thick sequences of Eocene to Miocene limestone and dolomitic limestone formations — including the Ocala Limestone and Avon Park Formation — rich in calcium carbonate. These soluble carbonate rocks dissolve as groundwater percolates through, releasing calcium and magnesium ions that produce the supply's characteristically hard, mineralized profile.
Hard water in Key West leads to scale buildup in pipes, water heaters, dishwashers, and coffee makers, reducing efficiency and lifespan. Faucets and fixtures develop limescale deposits, while laundry and dishes may appear dingy. Maintenance includes periodic vinegar soaks for removable parts, installing scale-inhibiting showerheads, and using rinse agents in dishwashers. A water softener is recommended for whole-house treatment. FKAA maintains EPA compliance including lead and copper rule adherence; Consumer Confidence Reports (2023–2025) show no PFAS detections above limits; treatment includes lime softening, chloramination, and filtration; pH is typically 7.5–8.5; naturally occurring radium is monitored and managed through blending.
Geology & Source: Floridan Aquifer System — Eocene to Miocene limestone and dolomitic limestone (Ocala Limestone, Avon Park Formation); carbonate dissolution releases calcium and magnesium, producing hard groundwater transported via 40-mile aqueduct to Key West
Other Florida Water Reports
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Frequently Asked Questions
Is Key West's water safe to drink?
Do I need a water softener in Key West?
How does Key West compare to the USA average?
Data Sources & Methodology
Water quality data for Key West 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.