How hard is the water in Robertson County, TN?
11.4 grains per gallon
A softener will pay its way here.
The median hardness measured in Robertson County, TN is 194 mg/L as calcium carbonate, which is 11.4 gpg. That is very hard on the USGS scale. It comes from 245 samples at 36 sites between 1999 and 2018, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 10.5 and 12.3 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 11.4 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 Robertson 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 5.1 to 23.7 gpg
The softest single sample on record in Robertson County was 87.5 mg/L and the hardest 405 mg/L, a 5-fold gap. The top quarter of sites read above 12.3 gpg and the bottom quarter below 10.5 gpg.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 248 lb of salt a year (7 bags of 40 lb, about $45), 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 $145 a year.
Sizing at 11.4 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 684 | 24,000 | 83 lb |
| 2 | 1,368 | 24,000 | 166 lb |
| 4 | 2,736 | 24,000 | 333 lb |
| 6 | 4,104 | 32,000 | 499 lb |
Robertson County against the rest of Tennessee
Among the 95 Tennessee counties with data, Robertson County is number 19 of 95 counting from the hardest. Across the whole country it is harder than 56% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Robertson County: Claiborne County (11.3), Trousdale County (11.6), Union County (11.7).