This paper presents an experimental setup to measure permeability evolution induced by mechanical loading. The experiment consists in pressurising a pipe-specimen. Internal pressure is used to load and to measure permeability. The external face of the pipe is accessible, so that leak paths can be localised and quantified. In order to avoid premature cracking of the specimen due to the device, sealing components were designed using Finite Element Analysis with respect to the stiffness of pipes to be tested. Although the current design is used here to test carbon composite pipes, it can be easily adapted to other materials. The design was validated by measuring permeability on an impermeable pipe. The experimental setup and method were applied to a composite filament-wound pipe. Results give substantial quantitative information on the relationship between the number of leak paths and the increase in material permeability.