How hard is the water in Cotton County, OK?

14 grains per gallon

A softener will pay its way here.

The median hardness measured in Cotton County, OK is 239 mg/L as calcium carbonate, which is 14 gpg. That is very hard on the USGS scale. It comes from 292 samples at 15 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 11.4 and 29.3 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 14 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 6.3 to 33.3 gpg

The softest single sample on record in Cotton County was 107 mg/L and the hardest 570 mg/L, a 5-fold gap. The top quarter of sites read above 29.3 gpg and the bottom quarter below 11.4 gpg.

What a softener would cost to run

For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 305 lb of salt a year (8 bags of 40 lb, about $55), 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 $155 a year.

Sizing at 14 gpg

Cotton County against the rest of Oklahoma

Among the 77 Oklahoma counties with data, Cotton County is number 35 of 77 counting from the hardest. Across the whole country it is harder than 66% of counties.

Softest in Oklahoma: McCurtain County at 0.8 gpg. Hardest: Greer County at 125 gpg. Closest to Cotton County: Texas County (14), Osage County (13.8), Ellis County (13.7).