The vertical discharge method is a process of discharging excess water in the ground to stabilize the ground. Among the vertical discharge methods PBD method is one of the most widely used. The discharge capacity of PBD decreases due to two main reasons. One is clogging of the filter and the other is reduction of the flow area of PBDs. PBDs usually consist of nonwoven filter and plastic core, which are deformed by soil pressure under the ground. In this study, the effects of the shape of core and tensile properties of filter on the discharge capacity were investigated. The deformation of the filter and core showed strong relationship to the discharge capacity. The filter was elongated and deformed at low pressure levels, and the core starts to deform at high pressure levels. Both deformations of the filter and the core decreased the discharge capacity.