One of the main components of hard water is caco3. when hard water evaporates, some of the caco3 is left behind as a white mineral deposit. plumbing fixtures in homes with hard water often acquire these deposits over time. toilets, for example, may develop these deposits at the water line as the water in the toilet slowly evaporates away. if water is saturated with caco3, how much of it has to evaporate to deposit 0.390 g of caco3? ksp for caco3 = 4.96 x 10-9.