How hard is the water in Miami-Dade County, FL?
14.9 grains per gallon
A softener will pay its way here.
The median hardness measured in Miami-Dade County, FL is 256 mg/L as calcium carbonate, which is 14.9 gpg. That is very hard on the USGS scale. It comes from 205 samples at 112 sites between 1990 and 2023, drawn from groundwater wells, which is what most taps and private wells in the county draw on.
How much it varies here
Half the sites came in between 13.2 and 49.9 gpg. The whole middle of that range gives the same answer, so a test of your own tap is unlikely to change it. Confidence in the county figure: high (how it is measured).
What to do next
At 14.9 gpg a softener pays its way here. Before you buy, check the quoted unit's grain capacity against the sizing table below, and ask whether it regenerates on demand, which uses less salt than a timer. Call your utility for its own report if you are on city water.
More on sizing a softener for your household.
From 11.2 to 285.7 gpg
The softest single sample on record in Miami-Dade County was 191 mg/L and the hardest 4,890 mg/L, a 26-fold gap. The top quarter of sites read above 49.9 gpg and the bottom quarter below 13.2 gpg.
Wells 14.9 gpg, rivers and lakes 13.4 gpg
205 groundwater samples from 112 wells put the median at 255.5 mg/L. 2,530 surface samples from 206 sites put it at 229.5 mg/L. In Miami-Dade County the wells come out 1.5 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. The two sources are close, so the county figure should hold whichever one your tap is on.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 326 lb of salt a year (9 bags of 40 lb, about $59), and roughly 2,346 gallons of regeneration water. Installed, most units run $1,000 to $4,500; spread over 15 years with salt, that is about $159 a year.
Sizing at 14.9 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 894 | 24,000 | 109 lb |
| 2 | 1,788 | 24,000 | 218 lb |
| 4 | 3,576 | 32,000 | 435 lb |
| 6 | 5,364 | 40,000 | 653 lb |
Miami-Dade County against the rest of Florida
Among the 67 Florida counties with data, Miami-Dade County is number 21 of 67 counting from the hardest. Across the whole country it is harder than 69% of counties.
Softest in Florida: Washington County at 0.3 gpg. Hardest: Sarasota County at 32.2 gpg. Closest to Miami-Dade County: Pinellas County (15), Duval County (15.7), Orange County (15.8).