How hard is the water in San Joaquin County, CA?
9.5 grains per gallon
A softener is worth it here.
The median hardness measured in San Joaquin County, CA is 162 mg/L as calcium carbonate, which is 9.5 gpg. That is hard on the USGS scale. It comes from 358 samples at 156 sites between 1990 and 2023, 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 and 20.1 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 9.5 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 San Joaquin 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 0.6 to 138.4 gpg
The softest single sample on record in San Joaquin County was 10.1 mg/L and the hardest 2,370 mg/L, a 235-fold gap. The top quarter of sites read above 20.1 gpg and the bottom quarter below 5 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 9.5 gpg, rivers and lakes 8.7 gpg
358 groundwater samples from 156 wells put the median at 162 mg/L. 478 surface samples from 12 sites put it at 149 mg/L. In San Joaquin County the wells come out 0.8 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.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 207 lb of salt a year (6 bags of 40 lb, about $37), 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 $137 a year.
Sizing at 9.5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 570 | 24,000 | 69 lb |
| 2 | 1,140 | 24,000 | 139 lb |
| 4 | 2,280 | 24,000 | 277 lb |
| 6 | 3,420 | 24,000 | 416 lb |
San Joaquin County against the rest of California
Among the 58 California counties with data, San Joaquin County is number 26 of 58 counting from the hardest. Across the whole country it is harder than 49% of counties.
Softest in California: Sierra County at 1.7 gpg. Hardest: Calaveras County at 98.3 gpg. Closest to San Joaquin County: Imperial County (9.5), Humboldt County (9.3), Mendocino County (9.2).