Water hardness in Key West
5.7 gpg moderately hard
Tap water in Key West is moderately hard: 5.7 gpg (97 mg/L · 5.4 °dH · 9.7 °fH).
Source: FKAA Drinking Water Standards & Analyses 2016 (2016) · data checked 2026-11-02
This figure is over 3 years old; hardness may have changed.
Key West is served by the Florida Keys Aqueduct Authority. Its 2016 analyses list hardness at 97 mg/L as CaCO3, which is moderate. That figure is ten years old, so treat it as an estimate and check the current FKAA report.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 5.7 gpg |
|---|---|
| Utility | Florida Keys Aqueduct Authority |
How Key West compares
- Tap water in Key West is 37 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1037 of 1372 in the United States (1 = hardest); 24 % of these cities have softer water.
- In Florida it is number 15 of 17 cities; the regional median is 8.2 gpg.
Ranking of the hardest and softest water in the United States →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Key West
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Key West water hard or soft?
It is moderately hard: 97 mg/L as CaCO₃ (5.7 gpg, 5.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Key West safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Key West water?
5.7 gpg, equal to 5.4 °dH, 9.7 °fH or 97 mg/L calcium carbonate.
What dishwasher salt setting should I use in Key West?
For 97 mg/L (5.4 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Key West?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: FKAA Drinking Water Standards & Analyses 2016 (2016). Method: figure published by the water supplier. FKAA Drinking Water Standards & Analyses 2016 · Outdated figure? Tell us