Recently, the management of water resources become more important due to the climate change. The ISO 14046 guideline for estimating water footprint, has been published according to global trend. In this study, we analyzed results of water footprint assessment on an water purifier product in life cycle. The usage of drinking water was a major environmental key factor in the evaluation of the water availability footprint, and the parts consisted of product was caused by environmental key factor in the evaluation of the eutrophication. Also, it was analyzed that the use of drinking water at the use stage and the consumption of electricity were main environmental key factors in the evaluation of the acidification. This results of the water footprint assessment have meanings of considering the water availability footprint and the environmental impact of the water consumption in the life cycle of the water purifier system. It is necessary to simultaneously consider not only water consumption at the stage of use, but also parts of products.