Rainwater Collection

Abstract

To harvest rainwater in building, it is collected from the potential catchments of the building and its surrounding premises. The roof of a building serves as the most effective catchment, but in critical cases various other type of catchments are used. A collection system should be provided to collect rainwater from the catchments. Although roofs are mostly a flat and horizontal surface, roofs of various configurations and inclinations are also seen. As a result, the types of collection and collecting systems, due to roofs of varied shapes, configurations, and inclinations, also differ. The roofs of buildings are mostly made of reinforced cement concrete, but roofs of various other materials also exist. Roofing materials influence the quality of the collected rainwater. Various surface-finishing materials are sometimes used on roofs for various purposes, which also contribute to the quality of rainwater. After a considerable dry spell, the rainwater of the first rain is generally found to be comparatively more contaminated and polluted. Therefore, a considerable amount of such first rainwater must be flushed out. In this chapter, various catchments of buildings, particularly roofs of various designs and materials, as well as the collection approaches and first rainwater‒flushing methodologies, are discussed. Determining size of the rainwater-collecting elements, the volume of rainwater to be collected, and the quality aspects of the rainwater, is also discussed. Finally, ways of maximizing rainwater collection are suggested.