In the course of both preoperational testing and power operation of commercial nuclear power plants, water hammers of various component have been experienced with damage to the piping supports in at least one recent case. Water hammer is induced by pressure and momentum transient conditions generated in the piping by sudden changes to the flow conditions, and it is also produced by sudden valve opening or closure. Component in BWR and PWR such as SG has been found to be susceptible to these conditions. This study is concerned with the evaluation of the pressure and momentum transients resulting from sudden valve operation, and the determination of the dynamic response of the piping to the induced transient loading. In particular, the influence of change of fluid dynamic parameters on water hammer head has been investigated. Four systems are analyzed for the water hammer force; for one of the systems three modes of valve operations were analyzed for water hammer force.