Originally Posted by TopherM
I live in FL, where we have a limestone water aquifer and thus notoriously hard water. I currently use a teaspoon of gypsum in each batch to offset that issue.
Just to clarify, hardness is a measure of how much calcium and magnesium are in the water. Adding more calcium (gypsum is calcium sulfate) is increasing your hardness.
If your water hardness is mainly due to limestone (CaCO3), then a lot of the calcium and carbonate will precipitate out by heating/boiling the water, but it's hard to say much without seeing a water report that lists the relevant stuff.