This project is to modifiy the exsit project of 2*5TPH RO+EDI projection. 2*5TPH RO+EDI water plant found in running condition but due to high silica content (48 mg/L) at RO feed, both RO membrane and EDI fouling occurs. RO system can’t reduce the silica content in water to < 1 mg/L desired by EDI input and water with high silica enters the EDI unit and eventually silica fouling occurs. This high silica is reducing the lifetime of RO & EDI unit and eventually EGB and STG equipment is getting affected. The antiscalant chemical used before RO system is suitable to remove silica fouling. But as silica content in RO feed is high, this chemical unable to prevent RO membrane fouling. Periodic CIP to be carried out to prevent RO membrane and EDI fouling but too much CIP also reduce the lifetime of RO membranes. The new DM water systems design needs modification by incorporating a 2 x 8 m3/hr capacity RO system before existing RO feed that can remove reactive silica to an acceptable limit (2 mg/L) and rest amount of silica can be removed by existing RO system and thus plant performance can be maintained.