Abstract Hydraulic studies Wastewater Treatment Plants Works on field are complex and expensive. An alternative to have done these studies is by building a up a calibrated physical model to simulate the conditions of similarity to the prototype. The aim of this study was a physical modeling to simulate flow at UASB pattern and to observe whether or not agreement are found prototype with it. The methodology involved in the design, calculation of relative length relations and construction, using a reduced scale of 1: 8 between the