This project focuses on the investigation of the impact for flowing of water and air on the performance of a centrifugal pump. A test rig is used to study the effect of entering air in the suction line one the performance of a 1 hp centrifugal pump. This test rig consists of two acrylic tanks, about 3.5 m length pipes with elbows and joints for the pipe line construction, two inch diameter transparent PVC pipe with about 1 m length, 1700 rpm three phase electric motor, inverter, two Pressure Transducers and two flow control valves. Results show (H – Q), (eta – Q) and (shaft Power – Q) curves for the used pump in the discussed cases. From results, it can be found that as motor rotational speed increases, head and efficiency of pump increases. As mass of air entered the suction pipe increases, head and efficiency of pump decreases. All results are found to be compatible with the previous data.