- Availability: Common
The group head is the temperature-controlled portal between the boiler and the puck. Its shower screen disperses the brew water across the basket; its temperature stability (PID-controlled on modern machines) directly affects shot quality. Commercial Brooklyn bars usually run two- or three-group machines so multiple drinks can be pulled in parallel during morning rushes. The 'group' is also slang for the unit: 'pulled three on group two.'