The purpose of this paper is analyzing the effect of valve closure time on water hammer phenomenon with column separation in viscoelastic pipes by experiment and numerical solution based on the Discrete Free Gas Model. The results are following: (1) Duration of column separation, pressure spike, water hammer pressure and superposition pressure increase linearly with a decrease of valve closure time. (2) The velocity of the tip of the cavity at collapse is bigger than the one at occurrence. (3) There are little differences between the results of numerical solution with linear interpolation and with curved interpolation in characteristic method, if Courant number is near 0.7 and dividing number of pipe length is bigger than 100. And both agree with the experimental results except pressure spike.
