How hard is the water in Polk County, IA?
21.6 grains per gallon
A softener will pay its way here.
The median hardness measured in Polk County, IA is 370 mg/L as calcium carbonate, which is 21.6 gpg. That is very hard on the USGS scale. It comes from 28 samples at 13 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 21 and 22.1 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 21.6 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.
More on sizing a softener for your household.
From 11.9 to 39.3 gpg
The softest single sample on record in Polk County was 203 mg/L and the hardest 672 mg/L, a 3-fold gap. The top quarter of sites read above 22.1 gpg and the bottom quarter below 21 gpg.
Wells 21.6 gpg, rivers and lakes 17.5 gpg
28 groundwater samples from 13 wells put the median at 370 mg/L. 395 surface samples from 16 sites put it at 298.8 mg/L. In Polk County the wells come out 4.1 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 32,000-grain unit covers a week between regenerations. Expect about 472 lb of salt a year (12 bags of 40 lb, about $85), 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 $185 a year.
Sizing at 21.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,296 | 24,000 | 158 lb |
| 2 | 2,592 | 24,000 | 315 lb |
| 4 | 5,184 | 40,000 | 631 lb |
| 6 | 7,776 | 64,000 | 946 lb |
Polk County against the rest of Iowa
Among the 93 Iowa counties with data, Polk County is number 34 of 93 counting from the hardest. Across the whole country it is harder than 87% of counties.
Softest in Iowa: Taylor County at 8.2 gpg. Hardest: Pocahontas County at 45.3 gpg. Closest to Polk County: Mills County (21.6), Story County (21.6), Marshall County (21.2).