The design of reverse osmosis and nano filtration plants is essentially influenced not only by the module arrangement, but also by the arrangement of the pressure vessel connections. Multifarious design possibilities can be considered as a result of many improvements introduced over the last few years. The key attributes is the three purposes port arrangement, feed-, concentrate- and permeate connection while comparing multiple port versus end port design. The following paper discusses the main factors for future plant design: Cost savings by reducing the complexity of stainless steel piping in multiple port design. The impact of the more compact design on total foot print required for the membrane plant, How can technical risks, especially corrosion, be considerably reduced, and The impact of the hydraulic design of the entire piping system and its influence on energy costs.