[Espeefan]

Trevor, these hydraulic systems usually run one of two ways. Either the hydraulic pump runs in reverse, to retract the cylinder, as is the case with the Wedico system, or else the pump only runs to extend the lift cylinder, and gravity is what retracts it back down to the collapsed position. These types of lift cylinders are single acting - which means it is pressurized from one port (end) only- it must rely on gravity, or some other force to retract it. I guess Wedico does a little of both. A pump running in reverse will draw the oil out, but gravity has a small role in it too. Doing it this way makes the system simpler, and cheaper, as no valves are needed.