At what minimum temperature is water considered 'hot water' for plumbing purposes?

Water is classified as 'hot water' for plumbing purposes at a minimum temperature of 120°F. This standard is important because it ensures that the water is sufficiently warm for various applications, such as sanitation, cooking, and cleaning. Water below this temperature may not effectively kill bacteria and other pathogens, which is a crucial consideration for health and safety in plumbing systems. Additionally, water at or above 120°F can better serve to dissolve detergents and improve the efficacy of cleaning processes.

The choice of 120°F is often used in plumbing codes and guidelines to balance efficiency with safety, as temperatures beyond this can also pose a risk of scalding. Hence, 120°F is established as a baseline for what constitutes hot water in residential and commercial plumbing systems.