How hard is the water in Williamson County, TN?
28.6 grains per gallon
A softener will pay its way here.
The median hardness measured in Williamson County, TN is 490 mg/L as calcium carbonate, which is 28.6 gpg. That is very hard on the USGS scale. It comes from 8 samples at 7 sites between 1990 and 2017, 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 9.5 and 46.5 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 28.6 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. Because Williamson 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 2.9 to 92.9 gpg
The softest single sample on record in Williamson County was 49.9 mg/L and the hardest 1,590 mg/L, a 32-fold gap. The top quarter of sites read above 46.5 gpg and the bottom quarter below 9.5 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 28.6 gpg, rivers and lakes 12.3 gpg
8 groundwater samples from 7 wells put the median at 489.5 mg/L. 440 surface samples from 49 sites put it at 210 mg/L. In Williamson County the wells come out 16.3 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 40,000-grain unit covers a week between regenerations. Expect about 625 lb of salt a year (16 bags of 40 lb, about $112), 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 $212 a year.
Sizing at 28.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,716 | 24,000 | 209 lb |
| 2 | 3,432 | 32,000 | 418 lb |
| 4 | 6,864 | 64,000 | 835 lb |
| 6 | 10,296 | 80,000 | 1,253 lb |
Williamson County against the rest of Tennessee
Among the 95 Tennessee counties with data, Williamson County is number 2 of 95 counting from the hardest. Across the whole country it is harder than 94% of counties.
Softest in Tennessee: Fayette County at 0.5 gpg. Hardest: Fentress County at 42.9 gpg. Closest to Williamson County: Marshall County (17.7), Maury County (17.2), Jefferson County (16.8).