Effective leakage models are crucial for leakage assessment and control strategies to improve the sustainability of vital water distribution, and other pipeline, infrastructure. This paper evaluates the interdependence of leak hydraulics, structural dynamics and soil hydraulics, particularly considering the significance of the soil conditions external to longitudinal slits in viscoelastic pipe. Initial numerical exploration and unique physical experimental results are presented exploring this complex physical phenomenon. The existence of an idealised fully restrained porous medium was shown to significantly increase the pressure- and time-dependent leak opening area whilst reducing the leak flow-rate, compared to a leak into water only. The research highlights the limitation of existing dynamic leakage modelling approaches which greatly simplify or neglect the influence of the soil conditions. Incorporation of this understanding into leakage modelling will enable more accurate estimation of leakage rates and hence the effects of management and control strategies.