Polyamine type polymer flocculants were synthesized and their characterization, viscosity and flocculation studies were conducted. In order to increase the molecular weight of polyamine flocculant which was prepared by polycondensation reaction from dimethylamine and epichlorohydrin, a small amount of 1,6-hexanediamine was employed. The incorporation of 1,6-hexanediamine up to 5.5mole% replacing corresponding part of dimethylamine gave a branched type polyamine sample with increased intrinsic viscosity ([η]=0.46 in 1wt% aqueous NaCl solution). The amount of 1,6-hexanediamine above 5.5mole%, however, resulted in gelation during polymerization. Utilizing raw water from Maegok potable water treatment plant, it was found that the addition of polyamine flocculant at a concentration of 1 mg/L level could reduce the amount of polyaluminum chloride (PAC) inorganic flocculant by half (15mg/L). It was also observed that the incoporation of polyamine flocculant at 1mg/L level was effective in the higher pH raw water, while PAC inorganic flocculating agent alone was not effective.