A coffee machine's group seal is a rubber ring located around the shower plate in the group head. In order to be airtight, the filter basket's lip is constructed to meet the group seal. This ensures that the coffee grinds get all of the water.
Even though it seems to be a minor component, a faulty or missing group seal may have catastrophic results. Water will seep into the drip tray if the portafilter seal is not watertight. Less water will be forced through the coffee beans at the appropriate pressure as a consequence, which will have an adverse effect on the quality of your coffee brew.
Maintaining your espresso machine's group seals is critical to its continued optimum performance. In order to keep your coffee machine operating smoothly and provide the finest cup of coffee, Barista Warehouse advises changing group seals every 3-6 months. The new group seals have a lot of natural flexibility and are pleasant to the touch. It is possible for coffee oils and residue to build up on the old group seals, which makes them less effective.
To help you out, certain commercial machines, like as the Gaggia and Costa, feature a flat and slightly ridged group seal. The flat side of the portafilter or filter holder should always be pointing downwards.