Key Largo Water Hardness & Quality Report (2026)
Water Hardness
15.7 grains per gallon
Source
groundwater
pH Level
8.5
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
836.8 mg/L
Est. Daily Cost
$0.72
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 Largo, your appliances are currently losing 36% efficiency due to mineral buildup.
| Appliance | In Key Largo | 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 Largo compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Key Largo, Florida | 268.5 mg/L | 11 ppt | 🔴 Very Hard | groundwater |
| Florida City, Florida | 272 mg/L | 11.1 ppt | 🔴 Very Hard | groundwater |
| Homestead, Florida | 92.5 mg/L | 5.5 ppt | 🟡 Moderately Hard | groundwater |
| Leisure City, Florida | 109.5 mg/L | 6 ppt | 🟡 Moderately Hard | groundwater |
| Naranja, Florida | 230.5 mg/L | 9.8 ppt | 🔴 Very Hard | groundwater |
National Benchmark
How Key Largo compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Key Largo | 268.5 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 Largo's Water Unique?
Local geology and source profile
Key Largo, Florida, in Monroe County — the northernmost Florida Key adjacent to Islamorada in Monroe County at the gateway to the Florida Keys — receives its water from the Florida Keys Aqueduct Authority (FKAA), drawing from the Florida City wellfield on the mainland through the Florida Keys aqueduct distribution.
The very hard 268.5 mg/L hardness and high TDS of 836.8 mg/L reflect the Monroe County supply's very hard calcareous island character — the Holocene Key Largo Limestone and Pleistocene Miami Limestone are calcareous formations in the Florida Keys carbonite platform; the FKAA supply travels through 130 miles of pipes from mainland Florida and picks up concentrated mineral content from the south Florida calcareous aquifer system (compare Islamorada FL: 264/824 in Monroe County comparable; Key West FL: 272/849 in Monroe County comparable; Key Largo consistent very hard from the same Monroe County FKAA wellfield Holocene calcareous supply). The Florida Keys supply — Holocene Key Largo Limestone (calcareous — primary hardness contributor), Pleistocene Miami Limestone (calcareous — secondary contributor), and Quaternary Florida Keys coralline sediment (calcareous — TDS contributor).
At 268.5 mg/L with TDS 837, Key Largo's water is very hard — a water softener is strongly recommended to protect plumbing and appliances. The PFAS level of 11.0 ppt is very high — a certified filter with PFAS removal is strongly recommended. Review the Florida Keys Aqueduct Authority's annual water quality report.
Geology & Source: Key Largo in Monroe County draws from the Florida Keys Aqueduct Authority on the Florida City wellfield (Monroe County, Florida Keys) — the Florida Keys limestone draws from Holocene Key Largo Limestone (calcareous) and Pleistocene Miami Limestone (calcareous) — Florida Monroe County FKAA wellfield Holocene calcareous supply produces very hard water at 268.5 mg/L with TDS 836.8 mg/L.