How hard is the water in San Miguel County, NM?
6.6 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in San Miguel County, NM is 113 mg/L as calcium carbonate, which is 6.6 gpg. That is moderately hard on the USGS scale. It comes from 715 samples at 121 sites between 1990 and 2023, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 4.5 and 12 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 6.6 gpg this is your call. Look for white film on glasses and crust on the shower head: if you see little of either, you can live without one. If you do want one, a 24,000-grain unit is enough, so ask for that size rather than a bigger one. Because San Miguel 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 1.6 to 83.2 gpg
The softest single sample on record in San Miguel County was 27 mg/L and the hardest 1,425 mg/L, a 53-fold gap. The top quarter of sites read above 12 gpg and the bottom quarter below 4.5 gpg.
Wells 5.7 gpg, rivers and lakes 6.6 gpg
1 groundwater samples from 1 wells put the median at 97.4 mg/L. 706 surface samples from 117 sites put it at 112.5 mg/L. In San Miguel County the rivers and lakes come out 0.9 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. 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 144 lb of salt a year (4 bags of 40 lb, about $26), 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 $126 a year.
Sizing at 6.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 396 | 24,000 | 48 lb |
| 2 | 792 | 24,000 | 96 lb |
| 4 | 1,584 | 24,000 | 193 lb |
| 6 | 2,376 | 24,000 | 289 lb |
San Miguel County against the rest of New Mexico
Among the 33 New Mexico counties with data, San Miguel County is number 27 of 33 counting from the hardest. Across the whole country it is harder than 37% of counties.
Softest in New Mexico: Rio Arriba County at 2.3 gpg. Hardest: Chaves County at 116.2 gpg. Closest to San Miguel County: McKinley County (7), Hidalgo County (5.8), Grant County (7.8).