One of the most frequent causes of failure of earthen structures subjected to water seepage, such as pervious dams and embankments, is the internal erosion of particles developing into piping. Similar phenomena may also occur in permeable foundation soils under impervious dam structures. This study focuses on the design and set up of a new laboratory device for testing internal erosion and piping on the representative elemental volume and on the small scale.The possibility is given to investigate the influence of the stress state and of the flow path length and direction, with respect to the soil layers inclination, for given seepage conditions. The quantity of eroded particles and the pore pressure distribution along the flow path are measured during the process. The results of preliminary tests on glass beads samples, in unsaturated conditions and under unconfined seepage, allow for a first assessment of the device control and testing procedure.