How the E61 Brew Group Works: Thermosiphon, Pre-infusion & 3-Way Valve Explained Simply

The E61 group head is the mechanical heart of many portafilter espresso machines. Introduced by Faema in 1961, it keeps the brew water at temperature via thermosyphon without its own heating element, controls three valves through a single lever, and automatically pre-infuses the coffee before the full pressure of around 9 bar kicks in.

Move the lever yourself, change pressure and temperature, and watch what happens inside – the animation runs on its own, but you can step in at any time:

What is the E61 group head?

The E61 is a group head that Faema founder Carlo Ernesto Valente developed and patented in 1961. Its name refers to the total solar eclipse of 15 February 1961 – the year it launched. The Faema E61 was the first espresso machine with automatic pre-infusion, an electric pump, and a thermosyphon to manage the group head's temperature. These three innovations still define the design today. It became so influential that the E61 group is now built into countless machines from renowned manufacturers – among them Rocket Espresso, ECM, Bezzera, and Profitec.

The thermosyphon: temperature without its own heating element

The group itself has no heating of its own. Two lines connect it to the boiler or heat exchanger: hot water rises through the upper line into the group, cools slightly there, and flows back through the lower line. This natural circulation – the thermosyphon – keeps the heavy, chrome-plated brass group constantly close to brewing temperature. That gives you temperature stability from cup to cup, but it costs heat-up time after switching on, because the large metal mass first has to warm all the way through. Depending on the machine and the bean, the ideal brewing temperature for espresso is usually in the range of about 90–96 °C.

Lever, cam, and the three valves

The lever carries a cam – an oval metal disc that presses on the valves one after another as it turns. The lever has three positions:

• Down: Group off – the drain valve is open.
• Middle (rest): both sides are sealed shut – some baristas also use this in-between position for manual pre-infusion.
• Up: Brewing – water flows to the coffee.

Three valves work together here: the brew valve (top), the spring-loaded infusion valve (middle), and the 3-way (drain) valve (bottom). What's special: the infusion valve isn't controlled by the lever but by pressure itself – it opens only once a certain pressure is reached.

How a shot unfolds – step by step

1. Lifting the lever opens the brew valve, and the pump fills the pre-infusion chamber above the infusion valve.
2. Pre-infusion: the coffee puck is gently and evenly wetted at low pressure – this reduces channeling.
3. Once the pressure reaches around 4–6 bar, the spring-loaded infusion valve opens.
4. Pressure rises to the full brewing pressure of about 9 bar, capped by the expansion valve (OPV). The espresso flows, and the crema forms.
5. Lowering the lever closes the brew valve, and the 3-way valve releases the residual pressure from the puck into the drip tray – the typical short hiss at the end.

Why baristas value the E61

The E61 combines three strengths: temperature stability from the thermosyphon, gentle, automatic pre-infusion for more even extraction, and a robust, serviceable mechanism, proven over decades. Add to that the tactile feel of the lever, which many love as part of the espresso ritual. Honestly, the system also has two downsides: the large metal mass needs a certain heat-up time (often 20–30 minutes for full stability), and the group wants regular care – occasionally greasing the cam, replacing the group seal when needed, and backflushing after espresso shots.

Matching machines & further reading

Wondering which machine suits you? Many prosumer machines with an E61 group are heat exchanger (HX) or dual-boiler models. Dive deeper here:

• E61 technology in detail: the secret behind the chrome head
• Single boiler, heat exchanger & dual boiler – how the heating system affects your espresso
• E61 vs. saturated group head compared
• Group head technology at a glance (E61, saturated, hybrid)
• Discover heat exchanger espresso machines with an E61 group
• Discover dual-boiler espresso machines
• All interactive coffee tools & simulators at a glance

Frequently asked questions about the E61 group head

What does “E61” mean?

The “E” stands for eclipse, the “61” for the year 1961 – the total solar eclipse of 15 February 1961, the same year Faema introduced the machine.

Does every E61 have pre-infusion?

Automatic pre-infusion is built into the classic E61 group by design: water first fills the pre-infusion chamber and wets the puck before the spring-loaded infusion valve opens at around 4–6 bar. How pronounced the pre-infusion turns out depends on the specific machine and the water pressure.

How hot does an E61 brew?

The group itself doesn't heat; instead, the thermosyphon keeps it close to the boiler or heat exchanger temperature. Depending on the machine and recipe, typical brewing temperatures are around 90–96 °C. On heat exchanger (HX) machines, a short flush evens out the temperature before the shot.

How do I maintain an E61 group?

Backflush regularly, replace the group seal once it starts leaking, and occasionally grease the lever cam with food-safe grease so it keeps moving smoothly.

Which machines have an E61 group?

A great many prosumer machines, including those from Rocket Espresso, ECM, Bezzera, Profitec, and other manufacturers. Over the decades, the E61 has become a de facto standard. Browse our heat exchanger and dual-boiler machines.

Source

Primary source (inventor/manufacturer): the original patent for the E61 group head – US Patent 3’230’974, “Alternately seating valves” (inventor Ernesto Valente, Faema; filed 1961, granted 1966).