This study is to investigate the pressure wave characteristics and the absorption of maximum and minimum pressure generated by instantaneous valve closure at the end of the straightening copper piping system with and without a water hammer arrester. Experiments were conducted under the following conditions : initial pressure 1~5 bar, flow velocity 0.6~3.0 m/s, water temperature $20^{circ}C$ and air volume of water hammer arrester $80~180^cm^3$. Experimental results show that the optimum air volume of water hammer arrester is 110㎤.