The key terms you will hear in a coffee machine service. See also our guide to descaling and backflush.
- Group head
- The part of the machine where the portafilter locks in and hot water passes through the coffee.
- Group gasket
- The rubber ring that seals the portafilter against the group. It wears with time and causes leaks.
- Portafilter
- The handle holding the basket, filled with coffee and locked into the group.
- Basket (filter screen)
- The perforated metal filter inside the portafilter that holds the coffee.
- Pressurestat
- The switch that controls boiler pressure and turns the heating on or off.
- Pump
- The component that pressurises the water for extraction.
- Boiler
- The tank that heats the water and produces the steam.
- Solenoid valve
- The electrically controlled valve that opens and closes the water flow.
- Descaling
- Removing limescale from the machine water circuit.
- Backflush
- Cleaning the group by reversing water flow with a blind basket and a cleaner.
- Grind
- The size of the ground coffee particles. For espresso it is fine.
- Dose
- The amount of coffee put in the basket for each coffee.
- Tamping
- Pressing the ground coffee in the basket with a tamper for even extraction.
- Extraction
- The process in which hot water passes through coffee and takes flavour and aroma.