Orifices are hydraulic devices producing pressure drops or head losses in pipes ways. Flow velocity measurements at the upstream of orifices allow understanding the effect of given flow field on head losses, while downstream measurements provide information of orifice jet stability. The placement of an UVP sensor in the flow disturbs the surrounding velocities and thus the results. The research therefore focuses on the implementation of a non-intrusive velocity measurement using an UVP sensor located outside the pipe. A seeding method is needed to improve the signal quality and accuracy using hydrogen bubbles produced by electrolysis of the flowing water. Firstly, this research shows the flow velocities in the orifice jet, at the upstream and downstream of the orifice. Logically, the average jet velocities are higher than upstream or far downstream flow velocities. Then, pressure recordings show the asymmetry behavior of head losses for the tested orifice. Finally, the power spectra analysis of the pressure and kinetic energy at the same location are compared and show a slightly higher decrease of energy for kinetic energy. The results highlight that further experiments should be perform with higher acquisition frequency.