How Pump Machines Pre-Infuse
Wikipedia says it's more common for an electric pump to generate espresso pressure than a lever.1 A pump machine makes its soft start by changing what the pump does, or what the water passes through, at the start of the shot.
Pump, pause, pump
Some makers build the soft start as a short pump run followed by a rest. The Profitec Move manual describes it this way. With pre-infusion on, the pump runs for 3 seconds after you press a pull button. It then pauses for 8 seconds to fully saturate the coffee puck. After that the pump starts again and extracts at 9 bar.2
Those numbers belong to that machine's description. Your machine may use different ones.
Active and passive phases
The ECM Estetika manual gives the two stages names. In active pre-infusion, the pump runs for a set time to build pressure. In passive pre-infusion, the pump pauses for a set number of seconds while the water soaks the coffee.3
The words "active" and "passive" are that maker's labels. They tell you what the pump is doing, not how hard the water is pushing. If your manual uses other words, go by its descriptions.
A valve and line pressure
A second approach doesn't switch the pump on and off at all. La Marzocco says pre-infusion on its machines with this feature is activated by opening a valve, which lets a continuous flow of water at line pressure saturate the puck. Afterward the pump fully engages to its static pressure.4
"Line pressure" means the pressure of the water supply the machine is connected to. The page on plumbed-in pre-infusion goes into that.
Putting the three side by side
| Approach | What happens at the start | Source |
|---|---|---|
| Pump, pause, pump | Pump runs briefly, then rests while the puck soaks | 2 |
| Active then passive | Pump builds pressure, then pauses | 3 |
| Valve at line pressure | A valve opens and water flows continuously at line pressure before the pump takes over | 4 |
All three end in the same place. The pump delivers its full pressure and coffee flows. The Profitec manual puts that main stage at 9 bar.2
Why the shot timer may not match
The Profitec Move manual says the passive pre-infusion pause isn't counted in the shot time it stores. Shot time there is the total duration of pump activity.2 So if you time a shot by eye and compare it with the number on the display, don't expect them to match. Other makers may count it differently.
Where it starts
On the Profitec Move, the soft start begins when you press a pull button. The manual describes switching pre-infusion on or off for each shot button.2 That makes it a per-button choice on that machine.
What to do with this
Read the section of your manual on pre-infusion. It tells you whether your machine has the feature, whether it's switched on by default, and how to change it. If you can't find it, the maker's support page is the place to ask, not a forum thread. The settings page shows what a few manuals list.
To compare with machines that have no pump to pause, read about lever and spring machines.
Notes and sources
- Espresso, Wikipedia
- Profitec Move user manual, Clive Coffee
- ECM Estetika user manual, Clive Coffee
- Pre-Brew, Pre-Infusion, and Pressure Manipulation Explained, La Marzocco USA
More soft-start notes
What Is Pre-Infusion in Espresso?What the gentle first stage of an espresso shot is, what it's meant to do to the coffee puck, and how makers describe it in their own words.
Pre-Infusion Versus BloomingPre-infusion and a pour-over bloom both wet the coffee first, but they aren't the same step. Here's how the two terms differ and where each is used.
How Lever and Spring Machines Pre-InfuseWhat sources say about spring-piston lever machines, and what La Marzocco says about lever position and pre-infusion length on its Leva-X.