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Hydraulic transient, also called pressure surge or water hammer, is the means by which a change in steady-state flow and pressure is achieved. When conditions in a water distribution network are changed, such as by closing a valve or starting a pump, it generates a series of pressure waves. These disturbances propagate at the velocity of sound within the medium until they dissipate to the level of the new steady state by the action of some form of damping or friction. Transient events can introduce large pressure forces and rapid fluid accelerations into a water distribution system, which may result in pump and device failures, system fatigue or pipe ruptures, and even dirty water backflow/intrusion. Many transient events can lead to water column separation that can result in catastrophic pipeline failures. Transient events can cause health risks and may lead to increased leakage or decreased reliability. Thus, flow control actions are extremely important and have implications not only for the design of the hydraulic system but also for other aspects of system operation and protection. Problems such as selecting the pipe layout and profile, locating control elements within the system, formulating operating rules, as well as facing the ongoing challenges of system management are all influenced by the control system details. A rational and economical operation requires accurate data, carefully calibrated models, ongoing predictions of future demands and transient loading system responses, and correct selection of both individual components and remedial strategies. These design decisions cannot be considered an afterthought to be appended to a nearly complete design. Transient analysis is a fundamental and challenging part of rational network design. Transient-flow simulation has become an essential requirement for ensuring the safe operation of drinking water distribution systems. This article provides a basic understanding of the physical phenomena and context of transient conditions, presents practical guidelines for transient condition suppression and control, and compares the formulation and computational performance of widely used hydraulic transient simulation schemes. A detailed transient flowchart that offers a comprehensive guide to the selection of components for surge control and suppression in water distribution systems is also provided. Includes 25 references, tables, figures. See more