How hard is the water in Custer County, OK?
115.8 grains per gallon
A softener will pay its way here.
The median hardness measured in Custer County, OK is 1983 mg/L as calcium carbonate, which is 115.8 gpg. That is very hard on the USGS scale. It comes from 368 samples at 28 sites between 1990 and 2025, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 98 and 138.7 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 115.8 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 17.0 to 161.6 gpg
The softest single sample on record in Custer County was 290.5 mg/L and the hardest 2,767 mg/L, a 10-fold gap. The top quarter of sites read above 138.7 gpg and the bottom quarter below 98 gpg.
Wells 54.1 gpg, rivers and lakes 117.3 gpg
7 groundwater samples from 4 wells put the median at 926 mg/L. 361 surface samples from 24 sites put it at 2007.5 mg/L. In Custer County the rivers and lakes come out 63.2 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. A utility here that draws from the aquifer can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, the water is harder than a standard single tank handles in a week, so plan on a larger or twin-tank unit. Expect about 2,529 lb of salt a year (64 bags of 40 lb, about $455), 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 $555 a year.
Sizing at 115.8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 6,948 | 64,000 | 845 lb |
| 2 | 13,896 | twin tank | 1,691 lb |
| 4 | 27,792 | twin tank | 3,381 lb |
| 6 | 41,688 | twin tank | 5,072 lb |
Custer County against the rest of Oklahoma
Among the 77 Oklahoma counties with data, Custer County is number 4 of 77 counting from the hardest. Across the whole country it is harder than 99% of counties.
Softest in Oklahoma: McCurtain County at 0.8 gpg. Hardest: Greer County at 125 gpg. Closest to Custer County: Woods County (115.7), Dewey County (116.4), Payne County (111).