How hard is the water in Marshall County, TN?
17.7 grains per gallon
A softener will pay its way here.
The median hardness measured in Marshall County, TN is 302 mg/L as calcium carbonate, which is 17.7 gpg. That is very hard on the USGS scale. It comes from 49 samples at 24 sites between 1990 and 2016, 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 13.7 and 22.6 gpg. The whole middle of that range gives the same answer, so a test of your own tap is unlikely to change it. Confidence in the county figure: high (how it is measured).
What to do next
At 17.7 gpg a softener pays its way here. Before you buy, check the quoted unit's grain capacity against the sizing table below, and ask whether it regenerates on demand, which uses less salt than a timer. Call your utility for its own report if you are on city water.
More on sizing a softener for your household.
From 3.3 to 46.3 gpg
The softest single sample on record in Marshall County was 57.2 mg/L and the hardest 793 mg/L, a 14-fold gap. The top quarter of sites read above 22.6 gpg and the bottom quarter below 13.7 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 17.7 gpg, rivers and lakes 11.7 gpg
49 groundwater samples from 24 wells put the median at 302.3 mg/L. 76 surface samples from 16 sites put it at 200.5 mg/L. In Marshall County the wells come out 6.0 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 386 lb of salt a year (10 bags of 40 lb, about $69), 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 $169 a year.
Sizing at 17.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,062 | 24,000 | 129 lb |
| 2 | 2,124 | 24,000 | 258 lb |
| 4 | 4,248 | 32,000 | 517 lb |
| 6 | 6,372 | 48,000 | 775 lb |
Marshall County against the rest of Tennessee
Among the 95 Tennessee counties with data, Marshall County is number 3 of 95 counting from the hardest. Across the whole country it is harder than 78% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Marshall County: Maury County (17.2), Jefferson County (16.8), Hawkins County (15.2).