A consortium of membrane element suppliers (Consortium) developed a project, funded in part by the U.S. Bureau of Reclamation, to create a new element diameter standard. By establishing a standard element size that reflects consensus by several membrane element suppliers, reverse osmosis (RO)/nanofiltration (NF) system end users will be able to realize the maximum economic benefits of the larger diameter elements through use of competitive element bidding in their projects. A primary component of the Consortium project is the conduct of an economic analysis, regarded as accurate and unbiased by the general industry, to determine cost savings from systems designed using larger diameter elements for three broad applications (seawater, brackish groundwater and surface water desalting or reuse). The project takes into account element and vessel manufacturability, system design limitations, handling and capital cost reductions. Acceptance of the results of this project by a majority of players in the water treatment industry is key to meeting the project goals. In an attempt to accomplish this objective, the Consortium incorporated feedback from a broad range of industry stakeholders at key stages of the project. This was accomplished through a comprehensive survey made available to utility staff, industry engineers, and OEMs. A website was also developed to garner additional industry input. Significant dialogue was held with leading vessel manufacturers to determine engineering and manufacturing issues associated with large diameter pressure vessels, particularly for high pressure applications. The project findings, which included development of capital and total water costs for each of the three feedwater applications using 8-inch, 16-inch and 20-inch diameter elements, and recommendations are being widely disseminated within the general water treatment industry. Includes 3 references, table, figures.