How hard is the water in Rock County, WI?

20.4 grains per gallon

A softener will pay its way here.

The median hardness measured in Rock County, WI is 350 mg/L as calcium carbonate, which is 20.4 gpg. That is very hard on the USGS scale. It comes from 72 samples at 5 sites between 1990 and 2004, drawn from every sampling site in the county, wells and surface water together.

How much it varies here

Half the sites came in between 17.5 and 21 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: medium (how it is measured).

What to do next

At 20.4 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 15.8 to 21.0 gpg

The softest single sample on record in Rock County was 270 mg/L and the hardest 360 mg/L, a 1-fold gap. The top quarter of sites read above 21 gpg and the bottom quarter below 17.5 gpg.

What a softener would cost to run

For a household of 3, a 32,000-grain unit covers a week between regenerations. Expect about 447 lb of salt a year (12 bags of 40 lb, about $80), 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 $180 a year.

Sizing at 20.4 gpg

Rock County against the rest of Wisconsin

Among the 72 Wisconsin counties with data, Rock County is number 15 of 72 counting from the hardest. Across the whole country it is harder than 85% of counties.

Softest in Wisconsin: Vilas County at 1.4 gpg. Hardest: Calumet County at 28.4 gpg. Closest to Rock County: Green County (20.5), Winnebago County (20.7), Racine County (20.8).