An injection device for injecting a pressurized liquid into a preform and forming a container. The injection device including a piston device having a piston body and a piston head arranged to reciprocate in the piston body and to fluidly isolate an inner chamber of the piston device. The piston body having a recess portion defining a location where the piston head is not in liquid tight contact with the piston body such that liquid can flow from the inner chamber to a part of the piston body on an opposite the inner chamber. The injection device being arranged for driving the piston head in the recess portion in a clean-in-place (CIP) configuration.