Water and Energy Conservation of Rainwater Collection Systems on Building Roofs

Publisher Summary This chapter investigates the supply and demand of using collected rainwater for toilet flushing for different type of buildings in Hong Kong. The collected rainwater is insufficient for the demand of toilet flushing for the high-rise buildings. The supply might only cover 10% of the demand because the rainwater catching area is limited for high-rise residential buildings. For commercial buildings of fifteen to twenty-five storeys, the reliability of supply is found better than the high-rise domestic buildings. It is because the supply increases and the demand decreases compared with high-rise domestic buildings. However, the reliability of rainwater supply for small houses or buildings with large floor areas is very good. Although using larger rainwater collection tank can collect much water, it would not be practicable as it would occupy more space, and increase structure loading and construction cost. The flushing or irrigation system in a building cannot just rely on rainwater, but also on fresh water supply as well.