Flushing the Group
Espresso machine group heads are prone to an accumulation of coffee grinds covering the dispersion screen and the rubber gasket. You can significantly reduce this buildup of spent grinds by rinsing some hot water through the shower screen each time you remove the portafilter to prepare a new shot.
Volumetric machines can be programmed to flush the correct amount of water through the group. This speeds up the workflow because a barista can perform a group head flush with a single press of a button; the valve will automatically shut off the flow of water. This helps to reduce wastage, too. The heating of water is very energy intensive, so if you flush excessive amounts of water each day you will feel it in your next energy bill.