1. Demineralized water is that water which do not contain any dissolved cations, anions and salts in it. Demineralized Water can be obtained by passing the water through cation and anionic exchangers.

2. During the hardness treatment process, water is first passed through the cation exchange process. The water obtained after this process is free from mineral cations and is acidic in nature.

3. This acidic water is further passed through the anion exchange process where hydroxyl ions neutralize the H⁺ ions and de-ionize the water obtained.