Group gaskets (also referred to as a brew head gasket) sit up in the grouphead of your espresso machine, creating a watertight seal with the inserted portafilter basket. Heat, moisture, calcium, and coffee buildup will wear out the rubber over time, and its recommended they be changed once every three months.
HOW OFTEN SHOULD YOU REPLACE YOUR GROUP GASKET?
Espresso machine group maintenance services should be performed every 3 to 4 months or at the very least twice a year for lower volume shops. We recommend changing the gasket as well as the screen and screw in your group. The longer you wait the harder the group gasket can become.