With global population rising at unprecedented rates, wastewater volumes will consequently increase leading to a need for effective disposal options. Marine wastewater outfalls provide a solution to this. However, effectively managing the cost and design of these outfalls are imperative. This book presents a method that optimises the manifold pipe of a marine wastewater outfall under various hydraulic principles and cost considerations. Costing data from 37 international pipe supply companies, offering pipes of various diameters, were used to develop hybrid design equations for the three main materials used for outfall construction. These equations optimise the trade-off between pumping head and pipe size as well as the compromise between cost of material and favorable hydraulic characteristics. The resulting equations are very useful for outfall design, as over-sizing of a project can cost unnecessary amounts of money and under-sizing will not fulfill an outfall’s intended hydraulic purpose and will in turn increase the operational cost in terms of energy.