One of the most popular tools for dealing with the seepage problem in embankment dams is using different types and shapes of downstream drains. So, the paper presents a comprehensive study of the different drainage systems through such dams. Many earth dam models are investigated through the SEEP/W model representing different dimensions and geometry of downstream drains. A comparison is carried out between the present study and previous experimental and numerical studies and the results of the present study are almost close to the previous studies. The present work concludes that the most influential factor in a horizontal drain is the length, and the thickness has a negligible effect. The reasonable length ratio of a horizontal drain (L/B) is about 0.34 according to the minimum seepage. The angle of toe drains has a slight effect on the different seepage parameters. The performance of the inclined chimney drain is better than the vertical drain to control the seepage.