How hard is the water in St. John the Baptist Parish, LA?
8.2 grains per gallon
A softener is worth it here.
The median hardness measured in St. John the Baptist Parish, LA is 140 mg/L as calcium carbonate, which is 8.2 gpg. That is hard on the USGS scale. It comes from 111 samples at 32 sites between 1990 and 2022, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 6.8 and 17.1 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 8.2 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 St. John the Baptist Parish 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 0.2 to 32.0 gpg
The softest single sample on record in St. John the Baptist Parish was 3 mg/L and the hardest 548 mg/L, a 183-fold gap. The top quarter of sites read above 17.1 gpg and the bottom quarter below 6.8 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 0.2 gpg, rivers and lakes 9.9 gpg
6 groundwater samples from 3 wells put the median at 3 mg/L. 105 surface samples from 29 sites put it at 170 mg/L. In St. John the Baptist Parish the rivers and lakes come out 9.7 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. A utility here that draws from the aquifer 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 179 lb of salt a year (5 bags of 40 lb, about $32), 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 $132 a year.
Sizing at 8.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 492 | 24,000 | 60 lb |
| 2 | 984 | 24,000 | 120 lb |
| 4 | 1,968 | 24,000 | 239 lb |
| 6 | 2,952 | 24,000 | 359 lb |
St. John the Baptist Parish against the rest of Louisiana
Among the 64 Louisiana counties with data, St. John the Baptist Parish is number 31 of 64 counting from the hardest. Across the whole country it is harder than 43% of counties.
Softest in Louisiana: Lincoln Parish at 0.1 gpg. Hardest: St. Bernard Parish at 53.9 gpg. Closest to St. John the Baptist Parish: St. Mary Parish (8.2), Terrebonne Parish (8.5), Iberville Parish (7.8).