This paper firstly presents the need for the industry to focus on controlling the price of water. Secondly, since the paper focuses on low pressure hollow fibre membranes, the processes used for the manufacture of Memcor庐 membrane modules, from material preparation to packaging and testing are explained. Thereafter, through referencing the Memcor membrane module manufacturing process, an analytical model to determine the membrane module cost and membrane performance is presented. The model leads to the presentation of the Water Price Index (WPI) which is an index that evaluates the membrane module price against its design flux, expected life and efficiency. By targeting a low WPI, the water industry can control the price of water and water treatment equipment. Analysis indicates that membrane design flux and expected life are the key drivers in keeping a low WPI. The paper concludes after presenting results of a factorial study and recommending further research subjects.