Any change in the pipe discharge, caused by valve closure or shutting off the pump, results in fluctuations in velocity and pressure of the flow; which develops transient flow in the water conveyance system. This flow causes various risks by creating rapid and short waves. A model composed of a reservoir, a polyethylene pipe and check valve was made to examine hydraulic transient flow in branched pipe lines. The model was made in the laboratory of hydraulic and physical models of water science faculty in Shahid Chamran university. The experiment were done on different length and diameter ration of branch to mainline in a constant discharge of 4 lit/s. the data acquired of installed pressure transducers in different points of the model were used to demonstrate how pressure wave transformed and became transient and the results are presented in the following diagrams. As maximum and minimum pressures downstream the branches decrease significantly in compare with the system without branching, some equations were proposed for estimating the maximum and minimum pressures downstream the branches.
