In two previous papers [1,2] different energy recovery systems were analysed with respect to their overall life cycle costs. The core hydraulic system with pressure exchanger was identified as the most advantageous ERS concept, and the question of appropriate component design and system optimization was discussed. As a result, the advanced SalTec core hydraulic system was designed. Since May 2004, this System has been installed in a seawater reverse osmosis (SWRO) plant in Sharm El Sheikh (Egypt) and tested under field test conditions. The present paper describes the results of field tests that were carried out to demonstrate its operating reliability. Priority was given to the function test of the pressure exchanger and optimization of the pertinent control unit. Therefore the specific energy consumption and the mixing rates are reported as detected without any initial optimisation. Under steady-state operating conditions, the operating reliability was demonstrated by low-noise operation without pulsation and vibrations. In the course of tests involving transient operating conditions an automatic start and stop procedure was developed and stored as control programme, which makes it possible to start or stop all the components of the core hydraulic system automatically. The tests also included the simulation of emergency situations. It was shown in the course of these tests that the control unit is able to regulate or readjust the system under uncritical conditions and to protect the components in critical situations by means of an emergency safety routine.