Tap water for indoor plants.

Hey there, I have been using tap water for all of my house plants for years and years and it hasn't caused much of a problem at all...I moved to a new town where it seems like the tap water here is much harder? Looks like there are a lot of calcium and other minerals. It builds up all over my terra cotta pots and it may have killed off my african violets. First off, in worried it may cause a problem to plants that are less tolerable of these deposits, and it is very unsightly on the outside/tops/bottoms of the pots. So here's my question; is there a sustainable efficient way to somehow rid of these deposits in the water without spending too much? I know I can purchase regular spring and distilled water but I don't think I would consider doing that because I have over 130 house plants. I also do not have a rain water collecting system because I am living in a rental. I started collecting rain water in jars from downspouts but it is time consuming for the amount of plants I have to water. Is there any kind of mineral absorbing powder or fluid that you can dilute into jugs of water that will remove these deposits? Any advice will help. Thank you!