How hard is the water in Tuolumne County, CA?

2.8 grains per gallon

You do not need a softener here.

The median hardness measured in Tuolumne County, CA is 47 mg/L as calcium carbonate, which is 2.8 gpg. That is soft on the USGS scale. It comes from 49 samples at 13 sites between 2008 and 2018, 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 0.2 and 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: high (how it is measured).

What to do next

You can skip the softener. At 2.8 gpg the most a softener would fix is the odd water spot. If a salesperson in Tuolumne County says otherwise, ask to see their reading in grains per gallon and compare it with this one. Because Tuolumne County straddles a decision line, check your own tap with a $10 test strip before you spend anything.

More on when a softener is not worth it.

From 0.1 to 7.4 gpg

The softest single sample on record in Tuolumne County was 2.5 mg/L and the hardest 127 mg/L, a 51-fold gap. The top quarter of sites read above 6 gpg and the bottom quarter below 0.2 gpg.

Wells 2.8 gpg, rivers and lakes 0.2 gpg

49 groundwater samples from 13 wells put the median at 47.4 mg/L. 225 surface samples from 43 sites put it at 3.5 mg/L. In Tuolumne County the wells come out 2.6 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.

Tuolumne County against the rest of California

Among the 58 California counties with data, Tuolumne County is number 55 of 58 counting from the hardest. Across the whole country it is harder than 21% of counties.

Softest in California: Sierra County at 1.7 gpg. Hardest: Calaveras County at 98.3 gpg. Closest to Tuolumne County: Mariposa County (2.7), El Dorado County (2.6), Marin County (3.6).