Pressure loss refers to the reduction in pressure that occurs as fluid flows through a system, such as pipes or ducts. This loss can be caused by factors like friction, changes in elevation, and obstructions within the flow path. Understanding pressure loss is crucial for designing efficient systems in various applications, including plumbing and HVAC. In engineering, pressure loss is often quantified using the Darcy-Weisbach equation or Bernoulli's principle. These calculations help determine the necessary pump or fan power to maintain desired flow rates. Managing pressure loss ensures that systems operate effectively and meet performance requirements.