Researchers have been trying to develop techniques for early forecasting of the degradation process in pipe networks. Different Non Destructive Testing Techniques are used for detecting damages in a variety of materials and structures. Guided wave technique is a suitable non-destructive technique which can be used for pipe inspection by generating cylindrical guided waves. In this research, steel pipes are inspected using cylindrical guided waves. The purpose of this paper is to investigate the influence of flowing water through the pipe on the guided wave propagation in the pipe wall. Investigations are also carried out when the pipes are in open air which gives the traction-free boundary condition. It is also investigated whether the direction of the flow influences the propagation of the guided waves. Experimental V(f) curves are extracted from the received signals for defect free and defective pipe specimens and compared to study the effect of water flow on the strength and other characteristics of various guided wave modes.