Key Biscayne Water Hardness & Quality Report (2026)
Water Hardness
15.6 grains per gallon
Source
groundwater
pH Level
8.5
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
832.9 mg/L
Est. Daily Cost
$0.71
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 Key Biscayne, your appliances are currently losing 36% efficiency due to mineral buildup.
| Appliance | In Key Biscayne | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 3.7 yrs | 12 yrs | -69% |
| Water Heater | 5 yrs | 15 yrs | -67% |
Regional Water Comparison
How Key Biscayne compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Key Biscayne, Florida | 267.5 mg/L | 11 ppt | 🔴 Very Hard | groundwater |
| Miami, Florida | 137 mg/L | 6.9 ppt | 🟠 Hard | groundwater |
| Coconut Grove, Florida | 107.5 mg/L | 6 ppt | 🟡 Moderately Hard | groundwater |
| Little Havana, Florida | 185.5 mg/L | 8.4 ppt | 🔴 Very Hard | groundwater |
| Miami Beach, Florida | 85.5 mg/L | 5.3 ppt | 🟡 Moderately Hard | groundwater |
National Benchmark
How Key Biscayne compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Key Biscayne | 267.5 mg/L | 🔴 High |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Key Biscayne's Water Unique?
Local geology and source profile
Key Biscayne, Florida, in Miami-Dade County — a Miami-Dade County barrier island adjacent to Coral Gables and Miami Beach off the southeast Florida coast — receives its water from the Miami-Dade Water Sewer authority, drawing from the Biscayne Aquifer (Miami-Dade County) through the south Florida distribution.
The extremely hard 267.5 mg/L hardness and TDS of 832.9 mg/L reflect the south Miami-Dade County Biscayne Aquifer supply's extreme calcareous-saline character — similar to Florida City FL (272 mg/L/852 TDS), Key Biscayne's coastal barrier island position adds saltwater intrusion contributions to the Biscayne Aquifer's already high calcareous hardness from the Pleistocene Miami Limestone. The Biscayne Aquifer at Miami-Dade County — Pleistocene Miami Limestone (highly calcareous — primary hardness contributor), Pleistocene Fort Thompson Formation (highly calcareous — secondary contributor), and coastal saltwater mixing (chloride — major TDS contributor).
At 267.5 mg/L with TDS 833, Key Biscayne's water is extremely hard. A water softener is essential to prevent severe scale damage. A reverse osmosis system is required for drinking water. The PFAS level of 11.0 ppt warrants a certified drinking water filter — Homestead Air Reserve Base (Miami-Dade County) and south Florida industrial corridor contribute to Key Biscayne's elevated PFAS readings.
Geology & Source: Key Biscayne in Miami-Dade County draws from the Miami-Dade Water Sewer on the Biscayne Aquifer (Miami-Dade County, south Florida) — the Biscayne Aquifer at Miami-Dade County is developed in highly calcareous Pleistocene Miami Limestone and Pleistocene Fort Thompson Formation — Florida Miami-Dade County Biscayne Aquifer Pleistocene highly calcareous aquifer produces extremely hard water at 267.5 mg/L with TDS 832.9 mg/L.