Steady-state hydraulic computer models are commonly used by water utilities for design analyses and operations control related to water flow, pressure, and quality applications. Typical analyses using computer models include sizing pipes, estimating available fire flows, managing chlorine residuals, and minimizing water age. Transient hydraulic models, though used less frequently, can be used to: evaluate the potential effects of transient pressures on water system equipment and water quality; properly design surge control equipment; and, to establish system operation procedures that minimize the occurrence and magnitude of transient pressures. Analysis of pressure transients, often referred to as surge or water hammer analysis, is more complex than traditional steady-state hydraulic analysis and is consequently often neglected in favor of basic hand calculated estimations, traditional rules of thumb, and engineering judgment. However, development of new and improved transient analysis software and improved computer processor speeds have reduced the primary obstacles, namely the expense and difficulty of analyses, which often preclude the use of transient analyses in the design and operation of water system facilities. The use of transient hydraulic models in the design and operation of water systems and water system facilities is the focus of this paper, with an emphasis on the need for computer model analyses. Typical transient hydraulic analyses examples are provided to demonstrate the usefulness of this technology. Case studies are used to demonstrate why rules of thumb and basic hand calculations often cannot provide the basis for adequate transient control and optimized operating procedures. The case studies also provide examples of transient pressures that could be developed by inadequate or over-designed surge control equipment, which are often specified when transient computer model analyses are not performed, and can significantly worsen the original transient pressure problems. Includes 2 references, figures.