How hard is the water in St. Martin Parish, LA?
16.1 grains per gallon
A softener will pay its way here.
The median hardness measured in St. Martin Parish, LA is 276 mg/L as calcium carbonate, which is 16.1 gpg. That is very hard on the USGS scale. It comes from 16 samples at 16 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 12.6 and 18.2 gpg. The whole middle of that range gives the same answer, so a test of your own tap is unlikely to change it. Confidence in the county figure: medium (how it is measured).
What to do next
At 16.1 gpg a softener pays its way here. Before you buy, check the quoted unit's grain capacity against the sizing table below, and ask whether it regenerates on demand, which uses less salt than a timer. Call your utility for its own report if you are on city water.
More on sizing a softener for your household.
From 2.1 to 22.3 gpg
The softest single sample on record in St. Martin Parish was 35.6 mg/L and the hardest 381 mg/L, an 11-fold gap. The top quarter of sites read above 18.2 gpg and the bottom quarter below 12.6 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 16.1 gpg, rivers and lakes 5.2 gpg
16 groundwater samples from 16 wells put the median at 275.5 mg/L. 287 surface samples from 9 sites put it at 88.6 mg/L. In St. Martin Parish the wells come out 10.9 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 351 lb of salt a year (9 bags of 40 lb, about $63), 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 $163 a year.
Sizing at 16.1 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 966 | 24,000 | 118 lb |
| 2 | 1,932 | 24,000 | 235 lb |
| 4 | 3,864 | 32,000 | 470 lb |
| 6 | 5,796 | 48,000 | 705 lb |
St. Martin Parish against the rest of Louisiana
Among the 64 Louisiana counties with data, St. Martin Parish is number 14 of 64 counting from the hardest. Across the whole country it is harder than 73% of counties.
Softest in Louisiana: Lincoln Parish at 0.1 gpg. Hardest: St. Bernard Parish at 53.9 gpg. Closest to St. Martin Parish: Concordia Parish (16.1), Franklin Parish (15.7), St. Landry Parish (15).