The concept of greywater recycling and reuse has gradually become one of the most important strategies in water stressed countries. Due to a high population density and uneven rainfall distribution, the annual average rainfall distribution per capita in Taiwan is one fifth of the global average, which makes Taiwan a seriously water-stressed country. This study used the unit of a family of four as the target and reexamined the zoning concepts of water usage areas, followed by integrating pipeline configuration, water storage design and a filtering system to propose an Interior Customized Greywater System (ICGS) which is based on the application for the family unit. This system can be customized and flexibly adjusted according to household space. In order to verify the feasibility and viability of system, this study performed system configuration and design based on real cases and proposed three scenarios to simulate a 20 year life cycle for cost economic analysis. The result reveals that this system has a minimum payback period of 4 years and provides investment incentives. For regions or countries which have higher water cost or are more water stressed, ICGS can significantly improve the processing and utilization of water.