UNLOADER VALVES VACUUM TRUCK Showing all 2 results Unloader Valve – 22912A This is a pressure-actuated unloader that is designed for any pump that fits within the flow and pressure range of the unloader. Unloader Valve – 22973C The unloader is capable of handling one or more shut-off guns and should be run with no bypass (if the full flow from the pump is going through the unloader).