Are you buying this house? If so, you should have the water tested beforehand... Your home inspector should take care of that... You're worried about mineral content, but also other contaminants like bacteria you can have in your water... They'll give you a breakdown on the mineral content and the inspector can probably tell you what size softener you should have to overcome that...Water softeners come in all sort of "grain" sizes, but I have no idea what grain size is good for us. We have 2 people in the house, a couple of animals, and ideally, we'd like to push our underground sprinkling through the water softener as well. Is 30,000 grains enough?