A piston type energy recovery device (ERD) can reduce the power consumption of seawater desalination system effectively, but the necessity of the oil hydraulic actuator for the ERD weakens the economics of the device and brings peripheral issues such as increased footprint. In this paper, a water hydraulic actuator driven by the high pressure brine of the desalting system is proposed to resolve the above problem and applied in the piston type reciprocating-switcher ERD (RS-ERD) to testify its effectiveness. The superiority evaluation proves that a reduction of up to 90.3% of the driving power consumption can be obtained by using the water hydraulic actuator, whose capital and maintenance costs are significantly lower than that of the oil hydraulic actuator. The experiments in the emulate test platform show that the RS-ERD with the water hydraulic actuator is operationally feasible and achieves high energy recovery efficiency of above 97%, except the existence of pressure pulsation (23.1%) in high pressure brine stream. Additionally, long term demonstration in the nanofiltration desalination system proves that the RS-ERD with water hydraulic actuator has a good operational reliability whose pressure pulsation has been dramatically minimized to 33% while maintaining the efficiency as high as 96%. (C) 2015 Elsevier B.V. All rights reserved.