How hard is the water in Marion County, TN?

3.2 grains per gallon

You do not need a softener here.

The median hardness measured in Marion County, TN is 56 mg/L as calcium carbonate, which is 3.2 gpg. That is soft on the USGS scale. It comes from 13 samples at 10 sites between 1990 and 2025, 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 2.7 and 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

You can skip the softener. At 3.2 gpg the most a softener would fix is the odd water spot. If a salesperson in Marion County says otherwise, ask to see their reading in grains per gallon and compare it with this one. Because Marion 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 7.3 gpg

The softest single sample on record in Marion County was 6.7 mg/L and the hardest 125 mg/L, a 19-fold gap. The top quarter of sites read above 5 gpg and the bottom quarter below 2.7 gpg.

Wells 3.2 gpg, rivers and lakes 5.8 gpg

13 groundwater samples from 10 wells put the median at 55.5 mg/L. 458 surface samples from 54 sites put it at 99 mg/L. In Marion County the rivers and lakes come out 2.6 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.

Marion County against the rest of Tennessee

Among the 95 Tennessee counties with data, Marion County is number 66 of 95 counting from the hardest. Across the whole country it is harder than 23% of counties.

Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Marion County: Grundy County (3.3), Moore County (3.2), Scott County (3.3).