How hard is the water in Coffee County, TN?
3.7 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Coffee County, TN is 64 mg/L as calcium carbonate, which is 3.7 gpg. That is moderately hard on the USGS scale. It comes from 250 samples at 239 sites between 1990 and 2022, 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 1.3 and 8.7 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 3.7 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 Coffee 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 0.1 to 77.5 gpg
The softest single sample on record in Coffee County was 2 mg/L and the hardest 1,327.5 mg/L, a 664-fold gap. The top quarter of sites read above 8.7 gpg and the bottom quarter below 1.3 gpg.
Wells 3.7 gpg, rivers and lakes 5 gpg
250 groundwater samples from 239 wells put the median at 64 mg/L. 83 surface samples from 30 sites put it at 85.8 mg/L. In Coffee County the rivers and lakes come out 1.3 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 82 lb of salt a year (3 bags of 40 lb, about $15), 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 $115 a year.
Sizing at 3.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 222 | 24,000 | 27 lb |
| 2 | 444 | 24,000 | 54 lb |
| 4 | 888 | 24,000 | 108 lb |
| 6 | 1,332 | 24,000 | 162 lb |
Coffee County against the rest of Tennessee
Among the 95 Tennessee counties with data, Coffee County is number 62 of 95 counting from the hardest. Across the whole country it is harder than 25% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Coffee County: Lawrence County (3.6), Unicoi County (3.6), Scott County (3.3).