Pressure transients commonly occur in water distribution systems and can sometimes cause operational problems or system failure. Low pressure transients can cause distribution system contamination if pathways exist for potential contaminants to enter the system. Pathways might include leaks, air valves, and customer service connections. Transient analyses are needed during system design to understand the potential magnitude of pressure transients and, if necessary, to determine how they should be adequately controlled. A transient hydraulic analysis computer program is required to evaluate potential transient conditions in the system and to develop pressure transient control strategies. There are numerous equipment and operational alternatives available for hydraulic engineers to consider when developing a transient control strategy. The best alternative typically depends on the characteristics and transient constraints of the system. Includes 7 references, figures.