Positioning control valve device of a flow rate regulator of a process water circuit of a heating-process water system, having a process water control piston which is able to be actuated by a process water volumetric flow, and having a working cylinder for activating the process water control piston, in which positioning control valve device a separating element is disposed within the working cylinder so as to spatially separate a working space which is within the working cylinder and fluidically connected to the process water circuit, wherein - the working space is designed as a restoring element receptacle space, in which a restoring element for restoring the process water control piston from a control position to its resting position is accommodated, and which is fluidically connected to the process water circuit by means of at least one connecting line, - the separating element is disposed and designed so as to be displaceable within the working cylinder in such a manner that it reduces the working space as the restoring element receptacle space as much as possible when the process water control piston is displaced in accordance with its axial displacement direction to its maximum control position, as a result of which a dead space between a working cylinder housing of the working cylinder and the separating element within the restoring element can be reduced to the maximum, characterized in that - the working space is reduced by more than 90%, preferably by more than 95%, compared to its initial volume in the resting position of the process water control piston when the process water control piston is displaced in accordance with its axial displacement direction to its maximum control position, - the separating element can be displaced in its entirety by the process water control piston, - the separating element is completely inherently rigid, and - the separating element is designed on its outer circumference with sliding surfaces by means of which the separating element slides along the inner surfaces of the working cylinder housing. - the working space is designed as a restoring element receptacle space, in which a restoring element for restoring the process water control piston from a control position to its resting position is accommodated, and which is fluidically connected to the process water circuit by means of at least one connecting line, - the separating element is disposed and designed so as to be displaceable within the working cylinder in such a manner that it reduces the working space as the restoring element receptacle space as much as possible when the process water control piston is displaced in accordance with its axial displacement direction to its maximum control position, as a result of which a dead space between a working cylinder housing of the working cylinder and the separating element within the restoring element can be reduced to the maximum, characterized in that - the working space is reduced by more than 90%, preferably by more than 95%, compared to its initial volume in the resting position of the process water control piston when the process water control piston is displaced in accordance with its axial displacement direction to its maximum control position, - the separating element can be displaced in its entirety by the process water control piston, - the separating element is completely inherently rigid, and - the separating element is designed on its outer circumference with sliding surfaces by means of which the separating element slides along the inner surfaces of the working cylinder housing.