An Actiflo Clarifier is a water purification system designed by Veolia Water Solutions in Johannesburg, South Africa, to handle 10 ML of water a day. The tank is relatively large and made using thin plates reinforcement with stiffeners. For the current design, it is found that the plate thickness can be reduced considerable by adding horizontal or vertical stiffeners or a combination of both. The addition of stiffeners will increase the rigidity of the tank wall by increasing the moment of inertia of the combined section. For the design of tank walls with intermediate horizontal stiffeners, there is no simple formula available. This research is focused on investigating the optimal stiffeners locations, in attempt to reduce costs without compromising on the structural integrity. Specifically the investigation focused on investigating the optimal stiffener locations using the 200 x 75mm Parallel Flange. The robustness was tested by developing a conceptual design on AutoCAD inventor and conducting simulations of varying distributed load on a beam (i.e the Actiflo wall) with multiple supports (Stiffeners)