The shot under the group
The first Google result for “what is an E61 group head” on 10 October 2026 is a Reddit thread in r/Coffee titled “What is a E-61 Brew Head and what are it’s pros and cons?” A commenter says the group is there to stay close to the brew-water temperature. They say an E61 does that by letting water move slowly from the boiler, through the inside of the group, and back to the boiler. They also say that slow path can leave the group cooler, which is why people flush before a shot. This page does not publish a flush volume.
The photo is espresso leaving a chrome group into a cup. The photo at the top of this page is that kind of group with the portafilter locked in and a cup already on the grate. HomeBaristaMods does not label either machine as an E61 group.
The other groups they name
The same commenter names two other designs. One is a group with its own heater, and they give the Breville Dual Boiler as the example. The other is a saturated group, surrounded by brew-boiler water, and they give the GS/3 as the example. The photo is a shot running into a cup, with a tamper and a jar of beans beside the machine. Those names belong to the comment. This page does not rank the designs, and it does not call this machine a Dual Boiler or a GS/3.
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FAQ
What is an E61 group head?
A commenter on the r/Coffee thread says an E61 moves water slowly from the boiler, through the inside of the group, and back to the boiler. They say that path can leave the group cooler, which is why people flush before a shot. The photos show the chrome group and the cup under it. This site does not publish a flush volume.
Why do they mention a flush?
They say the passive loop loses heat, so the group can be cooler than the brew water unless you flush before the shot. The photo is espresso leaving the group into a cup. HomeBaristaMods does not say how much water to run, and it does not call the machine in the photo an E61.
What other groups do they name?
They name a heated group, with the Breville Dual Boiler as their example, and a saturated group, with the GS/3 as their example. The top photo is a chrome group with a portafilter and a cup on the grate. This page does not rank those designs or label the photographed machines.