Abstract: A liquid pump and control system for maintaining a predetermined level of liquid in a vessel comprising a liquid level sensing means, a variable displacement hydraulic pump, a control means connected to said liquid level sensing means and said variable hydraulic pump, a constant speed driving means connected to said variable hydraulic pump, a hydraulically actuated motor in fluid communication with said variable hydraulic pump and a liquid pump in fluid communication with said liquid vessel for evacuating fluid therefrom, said liquid pump connected and driven by said hydraulic motor. The liquid level sensing means within the liquid containing vessel determines the fluid level in the vessel, provides an electric signal to a variable displacement hydraulic pump which is driven by a constant speed electric motor. The variable volume output of the hydraulic pump is coupled to and drives the hydraulic motor at an RPM proportional to the pump volume.