Dispersion screens diffuse the group head water to spread evenly over the coffee in the portafilter basket. With time they become lose and blocked, and as such need replacing. This forms part of the yearly machine maintenance on most machine, however are common to change every 3-6 months on busy machines.

Generally, dispersion screens are replaced by removing the screw or bolt located in to center of the screen, attaching the shower screen to the shower screen holder, except for the case of E61 group heads in which the actual group head gasket holds up the dispersion screen in which the seal has to be removed to replace the seal.