Shower Screens
Shower screens diffuse the group head water to spread evenly over the filter baskets where the coffee is. With time 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.
Recently the importance of water distribution of the coffee puck has become highly discussed, and companies such as IMS have developed amazing shower screens which aid in the water distribution and reduce the amount of coffee oils generating back into the group. These have been quickly adopted by the speciality coffee world, and top end machine manufactures. Although, significantly more expensive, we believe these to be a worthwhile addition to any machine.
Generally, shower 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 seal holds up the shower screen in which the seal has to be removed to replace the seal.
It is sometimes easier to back-flush the machine (using back-flushing detergents) prior to removing the screen in order to remove the coffee residue which is sticky in nature.