A pilot control relay valve to change the directional flow of fluid to a piston (such as, for example, the piston of a chemical injection pump for injecting chemicals at a slow or rapid rate over a long period of time), but also allow the recovery of exhaust fluids under significant back pressure. The pilot control relay valve comprises an elongated valve member shiftable within a valve body between a first and second position. The first position allows communication of control fluid to a first pressure receiving surface while allowing exhausting of fluid from a third or opposing pressure receiving surface, thereby to initiate movement of the valve member against the back pressure of the exhaust fluid from its first position to a position equalizing the pressure acting on a second pressure receiving surface with the pressure of the control fluid, thereby causing the valve member to move to its second position. The valve member when it is in its second position allows communication with the third pressure receiving surface while allowing exhausting of fluid from the first pressure receiving surface for initially moving the valve member against the back pressure of the exhaust fluid from its second position while equalizing the pressure acting on the second pressure receiving surface to move the valve member to a position equalizing the pressure acting on the second pressure receiving surface with a pressure lower than the pressure of the control fluid for moving the valve member from its first position, whereby the operation is repeated ad infinitum. Piping is connected to threaded exhaust ports in the valve body to communicate exhaust fluid to a reservoir where it is collected under pressure for further use.