The group head gasket is the rubber ring that seals your portafilter against the machine during extraction. It's a wear part by design — expect to replace it periodically, not treat a worn one as a sign something else is broken.
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01Signs the gasket needs replacing
- Water or coffee spraying sideways from the portafilter during extraction
- Portafilter feels looser than it used to when locking in
- A hissing sound at the group head under pressure
- Visible flattening, cracking, or a shiny compressed ring on the gasket itself
02Find the correct replacement part
Gaskets are sized to your specific group head diameter (commonly 54mm, 58mm, or a machine-specific size) — check your machine's model number before ordering, since a slightly wrong size will not seal properly even if it appears to fit.
03Removing the old gasket
- Unplug the machine and let it cool completely.
- Remove the portafilter and locate the gasket seated in the underside of the group head.
- Use a flathead screwdriver or dedicated gasket removal tool to pry gently at one edge, then work around the ring to loosen it fully.
- Clean the group head thoroughly afterward — old coffee buildup in the gasket channel prevents the new gasket from seating flush.
Avoid this mistake
Don't dig, gouge, or force tools aggressively against the sealing surface while removing the old gasket — damage here can prevent even a brand-new gasket from sealing properly afterward.
04Installing the new gasket
- Press the new gasket into the channel, checking that it seats evenly all the way around with no twisted or raised sections.
- Reinstall the shower screen if you removed it, and let the machine sit for a few minutes before first use — some gasket materials benefit from settling before their first heat cycle.
- Test by locking in an empty portafilter (no basket, no coffee) and running the machine briefly. No spray or hissing at the group head means a good seal.
| Symptom after replacement | Likely cause |
|---|---|
| Still spraying at group head | Wrong gasket size, or debris left in the channel |
| Portafilter now very hard to lock in | Normal for a fresh gasket — should ease after a few uses |
| Seal fine at first, fails again within weeks | Check ramps/tabs on the portafilter itself for wear |
A gasket is one of the cheapest, most common repair parts on any portafilter machine — if in doubt, replace it before assuming something more expensive has failed.