In recent years, our life-styles based on the large-scale production and consumption exacerbated global warming and other environmental problems. The fluctuations of precipitation in each area of the world are becoming largely because of the impact of climate change. In the future, a large volume of water is needed for the maintenance of our quality of life in many modern cities. Therefore, it is very important to conserve water based on the efficient use of water resources by the reuses of water, the uses of rain water, and people's behavior of saving water, etc. On thinking about the saving water and efficient use of water resources at home, people need the accurate knowledge about the performance and function of recent sanitary system. Also, people need the accurate estimation of the water consumption in each use. Therefore, in this paper, the recent sanitary fixtures and water usage are described in each use, kitchen, bathroom, washing and wash basin, and toilet. According to the calculation technique of water demands that has been developed by us, the water consumption of the conventional sanitary fixtures was compared with the water consumption of the saving water sanitary fixtures. It was clarified the possibility of water conservation when the sanitary fixtures of saving water type were applied for the toilet and washing machine.