How hard is the water in Cobb County, GA?
2.1 grains per gallon
You do not need a softener here.
The median hardness measured in Cobb County, GA is 37 mg/L as calcium carbonate, which is 2.1 gpg. That is soft on the USGS scale. It comes from 55 samples at 25 sites between 1993 and 2026, 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 1.2 and 15 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
You can skip the softener. At 2.1 gpg the most a softener would fix is the odd water spot. If a salesperson in Cobb County says otherwise, ask to see their reading in grains per gallon and compare it with this one. Because Cobb 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 0.2 to 28.6 gpg
The softest single sample on record in Cobb County was 2.6 mg/L and the hardest 489 mg/L, a 188-fold gap. The top quarter of sites read above 15 gpg and the bottom quarter below 1.2 gpg. So even in a soft county, a handful of wells here produce water hard enough to scale a heater.
Wells 2.1 gpg, rivers and lakes 1.8 gpg
55 groundwater samples from 25 wells put the median at 36.7 mg/L. 945 surface samples from 40 sites put it at 31.3 mg/L. In Cobb County the wells come out 0.3 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. The two sources are close, so the county figure should hold whichever one your tap is on.
Cobb County against the rest of Georgia
Among the 159 Georgia counties with data, Cobb County is number 41 of 159 counting from the hardest. Across the whole country it is harder than 17% of counties.
Softest in Georgia: Richmond County at 0.2 gpg. Hardest: Glynn County at 13.6 gpg. Closest to Cobb County: Dooly County (2.1), Colquitt County (2.1), Burke County (2.2).