Parts Of An Espresso Machine (Glossary Of Terms You Need To Know)

Posted by Angela Franco on

Espresso machine with many parts



What the heck does any of that mean?

If you've never bought an espresso machine before and are considering getting one, a lot of the terms in the product descriptions probably sound like a foreign language.

Than can be frustrating when you're trying to decide which espresso machine is right for you.

That's why we've collected the most common terms you'll come across describing various parts of an espresso machine. We hope this glossary clears up any confusion.


Glossary: Different Parts Of An Espresso Machine


Basically, the boiler heats and holds the pressurized water coming from the pump. The size of the boiler is one of the main elements to consider when choosing an espresso machine.

The bigger the boiler, the more drinks the machine will be able to produce. However, a bigger boiler also needs more energy and time to heat all the water.


Dual Boiler

As the name implies, dual boiler machines have two separate boilers. The pump sends water to both.

One heats water to boiling, which is needed to steam milk. The other heats water to the brewing temperature.

Most dual boiler machines feature a PID (see below) or Digital Temperature Controller, in order to carefully control temperatures for both boilers.


E61 Grouphead

This is a large, mechanically operated three-way valve and it's a classic component of espresso machine design.

The E61 has a few distinct features. Most importantly, the whole grouphead is machined out of brass, providing high thermal inertia.

This means that, while it takes a long time to heat up and cool down, it easily holds that temperature once it’s ready. These groupheads require more active participation from the user.



The grouphead is the heart of the machine and it's the final stop for water as it moves through an espresso machine.

Located on the front of the machine, the grouphead brings water out of the machine and into the filter basket.

All groupheads involve four basic parts: a portafilter, a place for the portafilter to lock in, a way to activate the pump, and a pathway for the water to move from the boiler to the portafilter.

The number of groups you need depends on how many baristas will be operating the machine, and of course, how many cups of coffee you need to produce daily. 


Heat Exchanger

Single boiler machines can only heat water to one temperature at any given time (see below for more), but you need boiling water for the steam and water that is not boiling to brew.

This means you have to first heat the brewing water in order to pull a shot, then wait for the water to reach the boiling point in order to produce steam. If you want to pull a shot again, you have to wait once more for a new boiler full of water to heat to the brewing temperature.

The heat exchanger solves this problem.

A second water line runs from the pump, but it does not feed into the boiler like the first. Instead, it passes through the body of the boiler inside a copper tube.

This copper tube is the heat exchanger.

The steaming water in the steam boiler heats the water in the heat exchanger, but does not bring it all the way to a boil. The brewed water never comes in direct contact with the boiler water.

The result is water at two temperatures, allowing you to pull shots and steam milk simultaneously.



PID stands for Proportional Integral Derivative. It is a simple computer that controls the heating element to keep the water at a set temperature. To do this, a PID is connected to the heating element and to a temperature probe inside the boiler.



Portafilter on espresso machine

The portafilter is a metal filter basket set inside a handle. It holds the ground and compressed coffee to be brewed.

There are different sizes of portafilters. 58 mm is the most common size for commercial machines. 53 mm is also widely used also produces excellent espresso. 


Rotatory Pump

This pump is mechanical. A motor spins a disc that is offset inside a large, round chamber. The spinning disc is segmented into sections by veins.

As the disc spins, the veins press against the wall of the outer chamber, diminishing the size of the section. This creates pressure.

Water is drawn in when the section expands and is pushed out as the section shrinks. Rotary pumps are quieter, offer more consistent pressure, and generally have longer lifespans than other types of pumps.


Single Boiler

The boiler has one heating element with two thermostats. One thermostat is set for a temperature range that is ideal for brewing coffee. The other is set at a temperature meant to boil water and produce steam.

You can either heat water to boiling, or to the brewing temperature, but not both at the same time.

As a result, a machine with a single boiler won't let you pull shots and steam milk at the same time. You have to wait for the water to reach the correct temperature when you change from espresso to steaming and vice versa.

The heat exchanger (see above) solves this problem.


Steam Wand

The steam wand is used to make milk-based beverages, like cappuccinos and lattes. As its name implies, it steams milk to get it textured and hot. 



A tamper for coffee

Tampers are tools used to pack espresso grounds into the basket of an espresso machine.

The purpose of a tamper is to pack the grounds evenly for a quality shot. A good tamper is made from lightweight metal and matches the size of the basket and portafilter you are tamping. 


Vibratory Pump

The vibratory pump is a small electromagnetic workhorse. A piston attached to a magnet is set inside a metal coil.

An electrical current runs through the coil causing the magnet to rapidly move the piston back and forth, pushing water through the machine. These kind of pumps are smaller, inexpensive and tend to be easier to replace.


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