Subject of the thesis is water hammer in pipe of constant diameter. The phenomenom is solved using software VODU with the method of characteristics. In the beginning of the thesis there are derivations which we need for calculating the hammer. Equation of continuity and dnymaic equation adapted for one dimension along the length of the pipe are used for calculation. Following the equations there is description of the computer code which is used in the software since it was, for the purpose the thesis, transformed from Basic to Visual basic. User interface and an example of software usage are also shown. In the last part thesis analyses impacts of different parameters on the size of over- and subpressures. It turns out that we can decrease the size of the water hammer in the most impactful way with slower closing of the valve.