How does Key Largo's water compare to the national average?

The USA national average is 151 mg/L. Key Largo (≈ 180+ mg/L) is 189 mg/L harder than average.

Key Largo Water Hardness & Quality Report (2026)

Water Hardness

very hard

180+ mg/L

Very Hard

estimated · not lab-verified

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

$0.91

energy & soap waste

Source: See methodology section below · Updated 2026

very hard180+ mg/LVery Hard · est.

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 45% efficiency due to mineral buildup.

Appliance	In Key Largo	Soft Water City	Efficiency Loss
Kettle	4.7 yrs	8.5 yrs	-45%
Washing Machine	6.6 yrs	12 yrs	-45%
Water Heater	8.3 yrs	15 yrs	-45%

Regional Water Comparison

How Key Largo compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Key Largo, Florida	≈ 180+ mg/L	11 ppt	🔴 Very Hard	groundwater
Florida City, Florida	≈ 120–179 mg/L	52.8 ppt	🟠 Hard	groundwater
Homestead, Florida	≈ 120–179 mg/L	122.6 ppt	🟠 Hard	groundwater
Leisure City, Florida	≈ 120–179 mg/L	6 ppt	🟠 Hard	groundwater
Naranja, Florida	≈ 120–179 mg/L	9.8 ppt	🟠 Hard	groundwater

National Benchmark

How Key Largo compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ Key Largo	≈ 180+ mg/L	🔴 High
USA National Avg	151 mg/L	🟠 Moderate
Scarsdale Top Rated	0.02 mg/L	🟢 None

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What Makes Key Largo's Water Unique?

Local geology and source profile

Source: GroundwaterTDS: 836.8 mg/LpH: 8.5

The Florida Keys Aqueduct Authority (FKAA) is the main water provider for Key Largo and the surrounding Florida Keys. Its sole water source is the Floridan Aquifer, which supplies groundwater through a large pipeline system to Monroe County. The FKAA monitors and treats water across its service area, with annual reports and sampling data available on its website.

Key Largo's water originates from the Floridan Aquifer, a vast Tertiary-age carbonate formation of Eocene and Oligocene limestone and dolomite. This aquifer stretches across the Florida peninsula and into the Keys. Slightly acidic groundwater easily dissolves these carbonate rocks, leading to significant amounts of calcium and magnesium entering the water. Consequently, the FKAA's supply is naturally very hard, a common trait for groundwater in south Florida and the Keys.

Homeowners in Key Largo will likely notice scale buildup on fixtures, appliances, and pipes due to the very hard water. Devices like coffee makers, water heaters, and dishwashers are especially prone to mineral deposits, which can reduce their efficiency. You might see white or tan residue on faucet aerators, shower heads, and inside kettles. If scale becomes a nuisance, the FKAA suggests considering point-of-use water softeners or whole-house systems. Routine descaling with white vinegar is a simple maintenance step. The FKAA publishes annual water quality reports detailing specific parameters like pH, lead, and copper, and some of its supplies are softened to around 85 ppm.

Geology & Source: Floridan Aquifer; Eocene-Oligocene limestone and dolomite formations create very hard water

Other Florida Water Reports

Florida City

≈ 120–179 mg/L

🟠 Hard

Homestead

≈ 120–179 mg/L

🟠 Hard

Leisure City

≈ 120–179 mg/L

🟠 Hard

Naranja

≈ 120–179 mg/L

🟠 Hard

Report an Issue

Notice an error or missing data? Help us keep this page accurate. If you spot incorrect water hardness, outdated utility info, or missing details, please let us know.

All reports are reviewed by our team. Thank you for supporting data quality!

Frequently Asked Questions

Is Key Largo's water safe to drink?

Yes. Key Largo's water meets all federal safety standards. The hardness is ≈ 180+ mg/L (Very Hard), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in Key Largo?

At ≈ 180+ mg/L (Very Hard), Key Largo's water will cause significant limescale on kettles, washing machines, and water heaters. A water softener or descaler is strongly recommended to extend appliance lifespan and reduce energy bills by up to 45%.

How does Key Largo compare to the USA average?

The USA national average is 151 mg/L. Key Largo (≈ 180+ mg/L) is 189 mg/L above the national average. The softest major city is Scarsdale at just 0.02 mg/L.

Data Sources & Methodology

Water quality data for Key Largo is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.

Estimated

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.

Estimated

Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.

Estimated

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.

Measured

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.

Modelled

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.

Calculated

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.