A study on the synthesis of zeolite 4A using the bituminous coal fly ash from power plant was carried out. This study aims to investigate possibility for detergent builder with synthesized zeolite. It was examined at the crystallization conditions of atmospheric pressure and that of pressurization. The synthesized zeolite was proved to be Zeolite 4A type by means of the XRD and SEM analysis, and then the synthesized zeolite was used as an absorbent the remove the $Ca^{2+}$ ions in the water. In this study, commercial zeolite and synthesized zeolite reached equilibrium within 10 and 30 minutes respectively. The amount of $Ca^{2+}$ ions exchanged by the commercial zeolite, atmospheric pressure zeolite (zeolite A) and pressurized zeolite(zeolite PA) were 391mg/L(as $CaCO_3$), 323mg/L(as $CaCO_3$) and 355mg/L(as $CaCO_3$) respectively.