How hard is the water in Polk County, TN?
8 grains per gallon
A softener is worth it here.
The median hardness measured in Polk County, TN is 137 mg/L as calcium carbonate, which is 8 gpg. That is hard on the USGS scale. It comes from 13 samples at 8 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 2.3 and 15.5 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: medium (how it is measured).
What to do next
At 8 gpg a softener is worth getting, mainly to protect the water heater and cut soap use. Get at least two quotes, ask each installer what grain capacity they are fitting, and check it against the sizing table below. Because Polk 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 0.9 to 44.6 gpg
The softest single sample on record in Polk County was 15.2 mg/L and the hardest 763 mg/L, a 50-fold gap. The top quarter of sites read above 15.5 gpg and the bottom quarter below 2.3 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 8 gpg, rivers and lakes 1.2 gpg
13 groundwater samples from 8 wells put the median at 137 mg/L. 902 surface samples from 106 sites put it at 20.5 mg/L. In Polk County the wells come out 6.8 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. A utility here that draws from the river 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 175 lb of salt a year (5 bags of 40 lb, about $31), 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 $131 a year.
Sizing at 8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 480 | 24,000 | 58 lb |
| 2 | 960 | 24,000 | 117 lb |
| 4 | 1,920 | 24,000 | 234 lb |
| 6 | 2,880 | 24,000 | 350 lb |
Polk County against the rest of Tennessee
Among the 95 Tennessee counties with data, Polk County is number 41 of 95 counting from the hardest. Across the whole country it is harder than 43% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Polk County: Roane County (8), Cheatham County (8.2), Stewart County (7.6).