Geotextile tubes made of woven geotextile materials have been widely applied to dewater waste sludge such as digested bio-solids, sewage sludge, dredged materials, industrial solid wastes, fly ash and coal slurry. However, the dewatering process of single geotextile tubes is time consuming. Two methods to accelerate the dewatering process of slurry in geosynthetic tubes were studied using laboratory model tests. The first method was to stack one tube on top of another and use the weight of the top tube to preload the bottom one. The second method was the vacuum method proposed in this paper to use vacuum pressure to consolidate the slurry in the geosynthetic tube. A 2.0-mm-thick woven polypropylene geosynthetic sheet was selected for the geotextile tubes. The deformation, pore water pressure and tensile forces monitored during the model tests against time are presented and analysed in this paper. The properties of the soil after consolidation were also measured and compared. The model test data showed that the vacuum method resulted in a lower water content and higher deformation rate than the two-layer stacking geotextile tube method. Compared with the stacking method, the vacuum method could reduce the risk to the geotextile sheet from explosion.