How hard is the water in Davidson County, TN?
12.2 grains per gallon
A softener will pay its way here.
The median hardness measured in Davidson County, TN is 209 mg/L as calcium carbonate, which is 12.2 gpg. That is very hard on the USGS scale. It comes from 1,214 samples at 90 sites between 1990 and 2023, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 7.3 and 15 gpg. That spread crosses a decision line, so some homes here land on a different answer. A $10 test strip on your own tap settles it. Confidence in the county figure: high (how it is measured).
What to do next
At 12.2 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. Because Davidson County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on sizing a softener for your household.
From 0.1 to 33.5 gpg
The softest single sample on record in Davidson County was 0.9 mg/L and the hardest 573.5 mg/L, a 637-fold gap. The top quarter of sites read above 15 gpg and the bottom quarter below 7.3 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 11.2 gpg, rivers and lakes 12.2 gpg
2 groundwater samples from 2 wells put the median at 191.5 mg/L. 1,212 surface samples from 88 sites put it at 209 mg/L. In Davidson County the rivers and lakes come out 1.0 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. 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 267 lb of salt a year (7 bags of 40 lb, about $48), 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 $148 a year.
Sizing at 12.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 732 | 24,000 | 89 lb |
| 2 | 1,464 | 24,000 | 178 lb |
| 4 | 2,928 | 24,000 | 356 lb |
| 6 | 4,392 | 32,000 | 534 lb |
Davidson County against the rest of Tennessee
Among the 95 Tennessee counties with data, Davidson County is number 13 of 95 counting from the hardest. Across the whole country it is harder than 59% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Davidson County: Knox County (12), Wilson County (11.9), Rutherford County (11.8).