Efficient technologies for optimizing water use in multifamily buildings

Excessive water use in residential buildings often arises from design deficiencies and conventional sanitary installations, which hinder the adoption of integrated conservation strategies. This study evaluates a package of efficient technologies to optimize water use in a 10-story multifamily building in Cusco, Peru, combining graywater reuse,rainwater harvesting, dual-flush toilets, flow-regulating fixtures, and smart leak detection. A quantitative, non-experimental, cross-sectional, and descriptive design was applied over a 6-month period from October 2024 to March 2025, comparing baseline operation with the proposed efficient configuration. The results show that the combined system reduces both potable water demand and household expenditure, with average monthly water consumption and billing decreasing by approximately 22% and 41%, respectively, while more than 200 cubic meters of gray and rainwater were recovered for non-potable uses such as toilet flushing, washing, cleaning, and irrigation. The novelty of this work lies in the integrated assessment of multiple low-cost technologies under real operating conditions in a Latin American multifamily building, linking detailed consumption records with tariff structures and leak scenarios. These findings indicate that efficient technologies can significantly improve urban water management, support climate and resource policies and contribute directly to several United Nations Sustainable Development Goals, particularly SDG 6 (Clean Water and Sanitation), SDG 9 (Industry, Innovation and Infrastructure), SDG 11 (Sustainable Cities and Communities), SDG 12 (Responsible Consumption and Production) and SDG 13 (Climate Action).