As in many regions it is no longer possible to satisfy the growing demands for water by conventional methods an increased production of potable water from saline waters is called for, One option with growing importance is the desalination of seawater with reverse osmosis using decentralised desalination plants with a fresh water capacity of few hundred to few thousand m(3)/d. Requested are plants that are easy to handle, able to be operated unattended under rough working conditions and require the lowest possible pretreatment, Reverse osmosis plants designed in accordance to the "plug and play" approach and equipped with the open channel disc tube module type DT using selected membranes can meet the requirements of this application niche of desalination technology, Technical details of the module and this plant concept as well as operating results are discussed.