Measured, not modelled
Measured well-water hardness in Contra Costa County, California: the median of laboratory samples taken at real water wells, in grains per gallon and mg/L as CaCO3, with the number of wells behind the figure.
| Median hardness | 21.6 gpg — about 370 mg/L as CaCO3 |
| Rating | very hard (Water Quality Association scale) |
| Wells measured | 70 |
| Laboratory samples | 70 |
Source: Water Quality Portal (USGS & US EPA). Water Quality Portal (USGS NWIS + EPA STORET), characteristic 'Hardness, Ca, Mg', siteType Well. These are laboratory results at water wells in the public record — not municipal tap water and not a model. The figure is a county median: individual wells vary, and only a test on the property itself gives its reading. The full table for the state is at well water hardness in California, by county; the method is on the methodology page.
Ratings use the Water Quality Association scale, in grains per gallon (gpg); 1 gpg is 17.118 mg/L as CaCO3.
| Rating | Range |
|---|---|
| soft | 0 – 1 gpg |
| slightly hard | 1 – 3.5 gpg |
| moderately hard | 3.5 – 7 gpg |
| hard | 7 – 10.5 gpg |
| very hard | over 10.5 gpg |
Yes — the median of 70 laboratory hardness samples from 70 measured wells in Contra Costa County is 21.6 grains per gallon (about 370 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
At or above 7 grains per gallon a water softener is the standard treatment; the county median of 21.6 gpg is above that line. Only a test on the property itself confirms the reading and sizes any equipment properly.
70 distinct wells in Contra Costa County carry a laboratory hardness result in the public record we read; a county is published only when at least 3 do. Nothing here is estimated from municipal tap water.
Selling water treatment here? The newly filed wells in Contra Costa County are sold as part of the Modesto – East Bay territory — one dealer, exclusive.
Built from the same data that qualifies every lead Hard Water Feed sells, and regenerated with it — the figures on this page change only when the underlying public record does.