How hard is the water in Decatur County, TN?
6.8 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Decatur County, TN is 117 mg/L as calcium carbonate, which is 6.8 gpg. That is moderately hard on the USGS scale. It comes from 82 samples at 19 sites between 1990 and 2019, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 1.4 and 7.6 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 6.8 gpg this is your call. Look for white film on glasses and crust on the shower head: if you see little of either, you can live without one. If you do want one, a 24,000-grain unit is enough, so ask for that size rather than a bigger one. Because Decatur County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on when a softener is not worth it.
From 0.4 to 21.6 gpg
The softest single sample on record in Decatur County was 6 mg/L and the hardest 370 mg/L, a 62-fold gap. The top quarter of sites read above 7.6 gpg and the bottom quarter below 1.4 gpg.
Wells 7.1 gpg, rivers and lakes 5.6 gpg
3 groundwater samples from 3 wells put the median at 121 mg/L. 79 surface samples from 16 sites put it at 96 mg/L. In Decatur 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 149 lb of salt a year (4 bags of 40 lb, about $27), 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 $127 a year.
Sizing at 6.8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 408 | 24,000 | 50 lb |
| 2 | 816 | 24,000 | 99 lb |
| 4 | 1,632 | 24,000 | 199 lb |
| 6 | 2,448 | 24,000 | 298 lb |
Decatur County against the rest of Tennessee
Among the 95 Tennessee counties with data, Decatur County is number 46 of 95 counting from the hardest. Across the whole country it is harder than 38% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Decatur County: Lake County (6.7), Giles County (7), Hamilton County (7).