Underground water has been used for living water source in Shimane University for 50 years since its establishment in the Nishi-kawatsu area. The building of the Faculty of Education in the University has become old,especially in the water service system. It has been easily assumed that the superannuated service main may have been the cause of deterioration of the water quality in the building. According to a preliminary examination, water quality of the tap water in the building indicated hard water property with extremely high conductivity of 715μ S/cm. Thus, a reverse osmosis filtration system (produced by Shimane Denko Co. by using a reverse osmosis membrane, ESPA^【〇！Ｒ】ESPAFREE 75 model, Nitto Denko Co.) has been employed for softening the hyper hard water in this study. Based on the sensory evaluation it was concluded that the resulting soft water with low conductivity of 22 μS/cm has good reputation.