How hard is the water in Charles County, MD?

0.3 grains per gallon

You do not need a softener here.

The median hardness measured in Charles County, MD is 5 mg/L as calcium carbonate, which is 0.3 gpg. That is soft on the USGS scale. It comes from 89 samples at 52 sites between 1990 and 2022, 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 0.1 and 0.8 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

You can skip the softener. At 0.3 gpg the most a softener would fix is the odd water spot. If a salesperson in Charles County says otherwise, ask to see their reading in grains per gallon and compare it with this one.

More on when a softener is not worth it.

From 0.0 to 13.7 gpg

The softest single sample on record in Charles County was 0.6 mg/L and the hardest 234 mg/L, a 390-fold gap. The top quarter of sites read above 0.8 gpg and the bottom quarter below 0.1 gpg. So even in a soft county, a handful of wells here produce water hard enough to scale a heater.

Wells 0.3 gpg, rivers and lakes 1.6 gpg

89 groundwater samples from 52 wells put the median at 4.9 mg/L. 44 surface samples from 24 sites put it at 27.9 mg/L. In Charles County the rivers and lakes come out 1.3 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. The two sources are close, so the county figure should hold whichever one your tap is on.

Charles County against the rest of Maryland

Among the 24 Maryland counties with data, Charles County is the softest. Across the whole country it is harder than 0% of counties.

Hardest: Washington County at 18.5 gpg. Closest to Charles County: St. Mary's County (0.7), Wicomico County (1.7), Anne Arundel County (2.1).