So you're doing two things by adding some of it to your must. First, you're increasing the net calcium ion load and thus increasing the hardness of the water.
I read this on another thread but did not want to hijack the thread. I am a little unclear about the hardwater issue. Is it a good thing or a bad thing¿ I have a well here and the water is fairly hard. Sometimes get what I think is a calcium build up on shower heads etc etc.
I have the Ozarka truck deliver water all of the time so I have good drinking water on hand at all times. The dogs dont mind it, I cook with it, I just dont drink with it.
Use it for mead/wine or no¿