Deuterium, an isotope of hydrogen, present in natural water in almost negligible amount but it is used for numerous purposes (both civil and defense). Special techniques are used to separate the negligible amount of deuterium contents from natural water and thereafter to 99.99 percent purity. Girdler Sulfide (GS) process is based on the exchange technique between two phases i.e. liquid (water) & gas (H₂S) and this technique was developed in 40's and also being used in the present era. The work is being done to analyze the performance of heavy water enrichment method based on original GS process termed as Liquid Feed Forward (LFF) and slight modification in the original design termed as Gas Feed Forward (GFF). The comparison on the material balance flow sheets, recovery, economy, efficiency and requirement of number of plates in both the processes is provided as adequate information to the readers to comprehend the differences in both the processes. In the original process i.e. LFF water is pumped directly to 2^nd stage from 1^st stage but in the modified design i.e. GFF water is not directly pumped to 2^nd stage from the 1^st stage and being circulated in a close cycle. The comparison is being done by the material balance results for both processes by keeping the recovery constant for both processes and determining the Number of Plates (N_p). For the recovery of 0.505 Kgmol/hr; N_p for 2^nd stage Hot Tower (HT) required was 91 and for 2^nd stage Cold Towers (CT) required was 55 for LFF and N_p required was 65 and 53 respectively for GFF. Hence it is possible to achieve the desired enrichment with slight modification and improvement in performance by adopting the GFF.