We explore the use of Granular Activated Carbon (GAC) as a mitigation technique for the treatment of drinking water that was artificially enriched with Rn-222 in laboratory by placing a radium rich granite stone (pitchblende) in a closed container filled with tap water for several days in order to allow Rn-222 concentration to approach its highest possible level. Granular Activated Carbon (GAC) was immersed into the water container in order to adsorb Rn-222 in radon-rich water. The optimum activation procedure for GAC preparation was determined. Suitable contact time and optimum quantities of GAC needed to reduce Rn-222 concentration in water were experimentally determined. There is a much greater increase in Rn-222 removal from water in the ranges from 1 part: 1000 parts to 4 parts: 1000 parts GAC/water ratios. Further increase in GAC/water ratio slowly affects the Rn-222 removal.