This course explores the critical but often overlooked relationship between water and energy consumption in the built environment, highlighting the environmental and economic impacts of inefficiencies in traditional hot water delivery systems. Attendees will gain foundational knowledge of hot water recirculation technologies, including key distinctions between traditional and on-demand systems, design considerations for new and retrofit projects, and performance optimization through smart technologies. Through a sustainability-focused lens, the course also addresses regulatory compliance, cost-benefit analysis, and occupant behavior, emphasizing how architects and engineers can play a leading role in water and energy conservation efforts. Real-world strategies and innovations will be presented to help professionals design and specify systems that enhance efficiency, occupant comfort, and environmental responsibility.