The water free from any mineral is called Deionised Water (D.M.Water). Naturally occurring water has various salts in dilute form which are called dissolved solids. When the water havingsuch mineral is required to be free from this, it is to be treated in Ion Exchange Resins column (H form) which converts all ionized salts to the equivalent acids. Now the acidic water is passed through Anion Resin Column (OH form) Which absorbs acids and water thus available is Demineralised Water. When the resins are exhausted the cationresin column is regenerated with HCL and Anion resin column is regenerated with NaOH solution. After regeneration now the plant will be in a position to give D.M. Water up to next regeneration.