How hard is the water in Terrebonne Parish, LA?
8.5 grains per gallon
A softener is worth it here.
The median hardness measured in Terrebonne Parish, LA is 145 mg/L as calcium carbonate, which is 8.5 gpg. That is hard on the USGS scale. It comes from 1,850 samples at 46 sites between 1998 and 2024, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 7.5 and 95.1 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 8.5 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 Terrebonne 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 0.4 to 249.1 gpg
The softest single sample on record in Terrebonne Parish was 6 mg/L and the hardest 4,265 mg/L, a 711-fold gap. The top quarter of sites read above 95.1 gpg and the bottom quarter below 7.5 gpg. So even here some sites draw water soft enough to need nothing at all.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 185 lb of salt a year (5 bags of 40 lb, about $33), 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 $133 a year.
Sizing at 8.5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 510 | 24,000 | 62 lb |
| 2 | 1,020 | 24,000 | 124 lb |
| 4 | 2,040 | 24,000 | 248 lb |
| 6 | 3,060 | 24,000 | 372 lb |
Terrebonne Parish against the rest of Louisiana
Among the 64 Louisiana counties with data, Terrebonne Parish is number 29 of 64 counting from the hardest. Across the whole country it is harder than 44% of counties.
Softest in Louisiana: Lincoln Parish at 0.1 gpg. Hardest: St. Bernard Parish at 53.9 gpg. Closest to Terrebonne Parish: St. James Parish (8.6), St. Mary Parish (8.2), St. John the Baptist Parish (8.2).