This article presents a literature review on rainwater usage in buildings in Brazil. It focuses on economic, environmental and social impacts. The legislation related to rainwater harvesting-including the cities that have made such a practice mandatory-was also assessed. The literature review was based on a search strategy that uses protocols to find and select studies about the main subject, i.e., rainwater harvesting in buildings. The protocols were defined as the site to be investigated (buildings), the intervention (rainwater harvesting), and the expected result (influence on the potable water consumption). Despite the variation of water availability in the country, it was concluded that there is a high potential for potable water savings when using rainwater in buildings in Brazil. Finally, it was observed the need for financial investments in experimental research and innovation technologies in order to improve rainwater management.

The objective of this work is to assess the impact of rainwater use in single-family houses on drinking water consumption and on the urban drainage system by means of a case study of a condominium of houses in the city of Curitiba, southern Brazil. A quantitative evaluation of the rainwater volume used and spilled in the recovery system was carried out using two methods for sizing the rainwater tank capacity. Using daily rainfall data and three demand scenarios of water consumption, it was possible to verify the efficiency and reliability of the adopted systems. Furthermore, in order to verify the impact on drainage, the greatest rainfall in the series was assessed and then it was possible to measure it by comparing the hydrograph peak flows with and without the rainwater harvesting systems in the watershed outfall, corresponding to the storage tanks (concrete boxes) in the condominium. It was concluded that there was a decrease in the peak flow of 4.9% and 4.4%, respectively, in the two storage tanks evaluated when the rainwater tank capacities were estimated using the method based on the German Practical Method.

The feasibility of installing rainwater harvesting systems in buildings is usually defined based primarily on economic analysis. In this perspective, we reviewed the literature related to water consumption in buildings, rainwater use, and environmental assessment tools to evaluate the impact of rainwater harvesting on the environment. Identifying water end uses in buildings showed a high potential for potable water savings through alternative sources (e.g., rainwater use for non-potable purposes). Most studies reviewed found potential for potable water savings from 20 to 65%. Moreover, the literature reported that rainwater harvesting systems might reduce the runoff volume from 13 to 91%. However, other possible benefits and impacts of the systems on water flow and the environment must be assessed in addition to the potential for rainwater harvesting. Life cycle assessment, life cycle cost assessment, and water balance modelling have been used in urban water management. Most life cycle studies reported that rainwater harvesting systems have better environmental performance than centralised systems. The water balance method may effectively determine the impacts these systems cause on the water cycle. Using life cycle assessment and the water balance method together is essential to evaluating rainwater harvesting systems integrated into the urban environment.

This article presents a literature review on rainwater usage in buildings in Brazil. It focuses on economic, environmental and social impacts. The legislation related to rainwater harvesting -including the cities that have made such a practice mandatory -was also assessed. The literature review was based on a search strategy that uses protocols to find and select studies about the main subject, i.e., rainwater harvesting in buildings. The protocols were defined as the site to be investigated (buildings), the intervention (rainwater harvesting), and the expected result (influence on the potable water consumption). Despite the variation of water availability in the country, it was concluded that there is a high potential for potable water savings when using rainwater in buildings in Brazil. Finally, it was observed the need for financial investments in experimental research and innovation technologies in order to improve rainwater management.

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