How hard is the water in Obion County, TN?
5.8 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Obion County, TN is 100 mg/L as calcium carbonate, which is 5.8 gpg. That is moderately hard on the USGS scale. It comes from 435 samples at 56 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 1.5 and 10.3 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 5.8 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 Obion 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 0.8 to 29.0 gpg
The softest single sample on record in Obion County was 13 mg/L and the hardest 496 mg/L, a 38-fold gap. The top quarter of sites read above 10.3 gpg and the bottom quarter below 1.5 gpg.
Wells 1.7 gpg, rivers and lakes 6.2 gpg
14 groundwater samples from 4 wells put the median at 28.3 mg/L. 421 surface samples from 52 sites put it at 105.5 mg/L. In Obion County the rivers and lakes come out 4.5 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. A utility here that draws from the aquifer can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 127 lb of salt a year (4 bags of 40 lb, about $23), 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 $123 a year.
Sizing at 5.8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 348 | 24,000 | 42 lb |
| 2 | 696 | 24,000 | 85 lb |
| 4 | 1,392 | 24,000 | 169 lb |
| 6 | 2,088 | 24,000 | 254 lb |
Obion County against the rest of Tennessee
Among the 95 Tennessee counties with data, Obion County is number 54 of 95 counting from the hardest. Across the whole country it is harder than 34% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Obion County: Clay County (5.8), White County (5.8), Pickett County (6).