Hard water causes many problems in domestic and industrial usage. The growing demands for water of high quality necessitate the development of modern and cost-effective technologies for softening hard and very hard waters. One of these techniques is the electrocoagulation process (EC). The purpose of this study was to investigate the efficiency of EC process in removal of water hardness through iron-rod electrodes in different circumstances. This study was conducted as a pilot plant. Experimental water sample was taken from water distribution network of Anar City located in northwestern part of Kerman Province, Iran. The indices for calcium and total hardness removal in pH (3.0, 7.0, and 10.0), electrical potential of 6, 12, and 24 V and reaction times of 10, 20, and 30 min were measured. The maximum efficiency of hardness removal which was obtained in pH 10.0, voltage of 12 and reaction time of 60 min are equal to 98.2% and 97.4% for calcium and total hardness, respectively. Final pH of remained solution has also increased which rises with acidic pH and decreases in alcoholic pH, so the results demonstrate the direct effect of pH, potential difference and reaction time on hardness removal using EC process. (C) 2010 Elsevier B.V. All rights reserved.