Rainwater Harvesting System (RWHS) for buildings: A mini review on guidelines and potential as alternative water supply in Malaysia

Malaysia receives an abundance of rain annually (≈ 2400mm/year). The country, however, is not excused from water crises such as floods and water shortages. According to the National Water Services Commission (SPAN) data, Malaysia water consumption in year 2021 is 201 LCD and may encounter a water shortage crisis if the situation is not improved in the future. Rainwater harvesting (RWHS) has great potential in tackling water shortages. It can also combat water scarcity holistically and reduce dependency on treated water from dam reservoirs. RWHS is a sustainable alternative to tackle water crises with minimal environmental impact. Currently RWHS used for non-potable purposes like cleaning, toilet flushing, and irrigation. Due to the nature of the catchment area, there are several ways in which contaminants can enter the rainwater system and compromise the water quality. Elements such as topography, weather, and pollution sources, have a direct impact on the quality of rainwater that is collected and stored. In addition to the non-potable uses, RWH has been used for potable water in countries such as Australia and Bangladesh, but the total number of uses is still very small. For potable use, regular monitoring is required because it poses a health risk due to the presence of chemical, physical, and microbiological contaminants. If the water quality parameters meet the acceptable levels of water supply, harvested rainwater could be used for drinking purposes in many countries in the future. To ensure consistently good water quality, it is essential to establish standard operating procedures and maintenance schedules based on water safety plan approaches for both household and institutional users. This paper aims to review existing management guidelines and explore potential technologies for rainwater harvesting in buildings across Malaysia.