How hard is the water in Calvert County, MD?
7.5 grains per gallon
A softener is worth it here.
The median hardness measured in Calvert County, MD is 128 mg/L as calcium carbonate, which is 7.5 gpg. That is hard on the USGS scale. It comes from 21 samples at 15 sites between 1990 and 2016, 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 5.9 and 13.6 gpg. That spread crosses a decision line, so some homes here land on a different answer. A $10 test strip on your own tap settles it. Confidence in the county figure: medium (how it is measured).
What to do next
At 7.5 gpg a softener is worth getting, mainly to protect the water heater and cut soap use. Get at least two quotes, ask each installer what grain capacity they are fitting, and check it against the sizing table below. Because Calvert County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on sizing a softener for your household.
From 0.2 to 161.2 gpg
The softest single sample on record in Calvert County was 3.2 mg/L and the hardest 2,760 mg/L, an 863-fold gap. The top quarter of sites read above 13.6 gpg and the bottom quarter below 5.9 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 7.5 gpg, rivers and lakes 3.2 gpg
21 groundwater samples from 15 wells put the median at 128 mg/L. 24 surface samples from 13 sites put it at 54.2 mg/L. In Calvert County the wells come out 4.3 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 24,000-grain unit covers a week between regenerations. Expect about 163 lb of salt a year (5 bags of 40 lb, about $29), 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 $129 a year.
Sizing at 7.5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 450 | 24,000 | 55 lb |
| 2 | 900 | 24,000 | 110 lb |
| 4 | 1,800 | 24,000 | 219 lb |
| 6 | 2,700 | 24,000 | 329 lb |
Calvert County against the rest of Maryland
Among the 24 Maryland counties with data, Calvert County is number 5 of 24 counting from the hardest. Across the whole country it is harder than 41% of counties.
Softest in Maryland: Charles County at 0.3 gpg. Hardest: Washington County at 18.5 gpg. Closest to Calvert County: Baltimore city (7.6), Carroll County (6.4), Montgomery County (6.4).