Sometimes you can remove them by palpation through the sublingual or parotid duct.<quoted text>
Salivary stones are made up of calcuim, phosphate, and carbonate ions among other substances. When their concentration rises above a critical threshold, they precipitate out. Water is intended to dilute them. Water with calcium, phosphate or carbonate will not do this as well. By analogy, if you were trying to dilute saltwater, you would use freshwater, not more saltwater.
They often go unnoticed until engorgement or xerostomia sets in.