How hard is the water in Marshall County, IA?
21.2 grains per gallon
A softener will pay its way here.
The median hardness measured in Marshall County, IA is 364 mg/L as calcium carbonate, which is 21.2 gpg. That is very hard on the USGS scale. It comes from 37 samples at 14 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 20.1 and 24 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 21.2 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 13.8 to 40.9 gpg
The softest single sample on record in Marshall County was 237 mg/L and the hardest 700 mg/L, a 3-fold gap. The top quarter of sites read above 24 gpg and the bottom quarter below 20.1 gpg.
Wells 21.2 gpg, rivers and lakes 20.7 gpg
37 groundwater samples from 14 wells put the median at 363.5 mg/L. 1 surface samples from 1 sites put it at 355 mg/L. In Marshall County the wells come out 0.5 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.
What a softener would cost to run
For a household of 3, a 32,000-grain unit covers a week between regenerations. Expect about 464 lb of salt a year (12 bags of 40 lb, about $83), 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 $183 a year.
Sizing at 21.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,272 | 24,000 | 155 lb |
| 2 | 2,544 | 24,000 | 310 lb |
| 4 | 5,088 | 40,000 | 619 lb |
| 6 | 7,632 | 64,000 | 929 lb |
Marshall County against the rest of Iowa
Among the 93 Iowa counties with data, Marshall County is number 36 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 Marshall County: Hancock County (21), Grundy County (20.9), Osceola County (20.9).