The growth of a single conduit in a gypsum layer located between two confined aquifers is studied using a continuum-pipe flow model (EVE). The initial diameter of the conduit and the exchange of water between the conduit and the gypsum layer are controlling factors at the initiation stage of conduit development. However they are unimportant in the long-term evolution of the conduit. Controlling factors at the later stages of conduit enlargement are identified using an analytical solution.