Water is the most vital of all our basic needs for survival. It is said that a person can go three weeks without food but only three days without water. Adding limestone to your well water balances the pH.
Adding limestone to water changes its chemical structure. Because the water we drink is not just H2O but also contains minerals and ions, it is important to balance them. Limestone acts as an alkaline to help balance the pH so that the water is less acidic.
More balanced pH can diminsh corrosion in plumbing and sink faucets.
You can't expect to pour limestone down your well and treat the water as ground water flows similar to a river. To add limestone or another alkaline, you will need a water treatment system.