Energy recovery device (ERD) is an important part of the seawater reverse osmosis (SWRO) desalina- tion system. There are principally two kinds of ERDs, the centrifugal type and the positive displacement (PD) type. The PD type is of extensive concern and is preferred in large-scale plants. In this article, an innovative fluid switcher was presented and a two-cylinder hydraulic energy recovery unit with a lab-scale fluid switcher was set up. Tap water was used as the working medium instead of the actual seawater and brine in SWRO desalination plants. Under steady state operating conditions, the experimental results were obtained on the variations of the pressure and flow rate to and from the energy recovery unit. The hydraulic recovery efficiency (EH) of the energy recovery unit with the fluid switcher reached up to 76.83%.