The group head gasket sits up in the group head, and provides the seal between the group and the basket lip.
The group head gasket may only last about 6 months, as the constant heat causes it to become brittle and this results in leaks from the portafilter when pulling a shot.
Here we show the replacement procedure for the Gaggia TS, but this will be identical for any of the Gaggia domestic machines, including the Classic and Baby.
Incidentally, the gasket is available in thicknesses of 8.5mm (standard) and 9.0mm (for older machines where wear of the group and portafilter needs to be taken up). The internal diameter is 56mm and the external diameter is 72mm. Different size gaskets are used for the Gaggia Cubika, Viva and Gran.
First remove the shower plate. This is normally held in place by a slotted or Philips screw, but these can be difficult to remove after a time, so it’s recommended to replace this with an allen screw.
With the shower removed, you can access the divider. Remove the two allen screws, and this will come away as well.
You can see below that the divider has been damaged by a previous attempt to remove the group gasket.
Finally, with care use an awl or a small screwdriver to lever out the old group gasket. It obviously does not matter if it is damaged, but make certain the slot in the group is clear of all remains. A mirror and a torch can be useful here.
You can see here that the old gasket has a noticeable wear groove and is very brittle.
Lubricate the new gasket with washing-up liquid, and insert it rounded surface upwards, inserting it into the slot starting at the front of the machine. With luck it will just push into place. If not, carefully work the gasket around, taking care to ensure the gasket fits squarely into the slot.
Using a blunt tool, working from the edges of the bulge, guide the remaining part of the gasket into place.
Reassemble and flush with water to remove traces of washing up liquid.