How hard is the water in Mendocino County, CA?
9.2 grains per gallon
A softener is worth it here.
The median hardness measured in Mendocino County, CA is 158 mg/L as calcium carbonate, which is 9.2 gpg. That is hard on the USGS scale. It comes from 74 samples at 50 sites between 1990 and 2020, 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 6.3 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: high (how it is measured).
What to do next
At 9.2 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 Mendocino 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 1.6 to 116.2 gpg
The softest single sample on record in Mendocino County was 27.8 mg/L and the hardest 1,990 mg/L, a 72-fold gap. The top quarter of sites read above 13.6 gpg and the bottom quarter below 6.3 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 9.2 gpg, rivers and lakes 4.9 gpg
74 groundwater samples from 50 wells put the median at 158 mg/L. 52 surface samples from 12 sites put it at 83.8 mg/L. In Mendocino 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 202 lb of salt a year (6 bags of 40 lb, about $36), 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 $136 a year.
Sizing at 9.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 552 | 24,000 | 67 lb |
| 2 | 1,104 | 24,000 | 134 lb |
| 4 | 2,208 | 24,000 | 269 lb |
| 6 | 3,312 | 24,000 | 403 lb |
Mendocino County against the rest of California
Among the 58 California counties with data, Mendocino County is number 29 of 58 counting from the hardest. Across the whole country it is harder than 48% of counties.
Softest in California: Sierra County at 1.7 gpg. Hardest: Calaveras County at 98.3 gpg. Closest to Mendocino County: Tulare County (9.2), Humboldt County (9.3), Imperial County (9.5).