Urbanization affluence, together with the impact of climate change, poses a significant threat to water resources. Future water crises must be solved in a sustainable manner. The aim of this research is to introduce a multi-demand water infrastructure for a regenerative houseboat. This research reflects a simulation study of four different greywater reusing scenarios. On-site water treatment units are selected as possible source-associated solutions for sustainability. The design for the multi-demand water system will be implemented into the houseboat structure located on the Kaiapoi River in New Zealand. The water infrastructure includes river water storage, roof catchment, and greywater and black water treatment units. The simulation for water infrastructure is created by EPANET under real-life conditions, using average household data for water consumption and wastewater discharge. The study uses the concept of reservoirs for water sources. The results from EPANET show that it is possible to simulate this infrastructure and provide a dynamic model for a real case scenario. It is explained that 12.1% of water is saved if toilet flushing alone uses treated greywater. If greywater is treated for reuse in the washing machine and shower, then 25.3% and 66.3% of water are saved, respectively. A portion of treated greywater can also be pumped to the water treatment unit for drinking purposes, thereby using zero water from a river source.