In this chapter, we will discuss the following key points: Concepts and standards of calculation of guaranteed regulation; water hammer phenomenon and objectives of studying water hammer; governing equations and wave speed of water hammer; analytical solution of single pipe water hammer; water hammer calculation for complex pipes; calculation of rotational speed rise; calculation conditions for water hammer; measures to handle the contradiction between water hammer pressure and rotational speed rise. Students should be acquainted with the concept and standards of the calculation of guaranteed regulation; master the calculation of the direct and indirect water hammer pressures in single pipe; master the calculation of water hammer pressure in complex pipes; master the calculation of rotational speed rise; be familiar with the measures to reduce water hammer pressure and control rotational speed rise.