Soil venting wells are difficult to analyse because flow occurs against a constant pressure. Here this difficulty is handled with a physically realistic but mathematically difficult nonlocal wellbore boundary condition ( BC). It is assumed that the air pressure inside the well is constant in space but time varying in an unknown fashion. A continuity equation is adopted at the boundary of the well which assumes the total well discharge consists of two parts: in flow from the surrounding unsaturated zone and release from wellbore storage. An efficient numerical algorithm is designed for dealing with the BCs at the well. The scheme is tested on two examples: the first is a simple problem with a known solution and the second problem is based on realistic data. The proposed method enables the accurate prediction of the time required to reach close to a steady state.