Strong wet seasons affect the stability of slopes as the pore pressure rises. One of the most effective methods used in the south of Chile, in fine soils, is horizontal drains. This method reduces the pore water pressure maintaining an adequate safety factor. A 3D seepage model is created to study the effects of horizontal drains on the pore pressure distribution under steady state conditions. Different physical approaches, that is, zero pore pressure and an input flow based on an energy balance, are studied to be able to represent the soil responds, decreasing the pore pressure due to the drains. This will allow considering adequately the influence of drains including aspects such as length, spacing, diameter and location of the openings of the drains.