The ECM Puristika Espresso Machine: How it works

ECM knows what’s important to the purist, which is why they created the Puristika — a single-boiler machine designed for those chasing purely excellent espresso. Unlike all other machines by ECM, it doesn’t include a steam wand, which leaves more room for details that matter to your shot of espresso, such as the built-in PID and expansion valve adjustment knob. We’re sure many questions are floating around about this adjustment knob — why did ECM put it on the front of the machine? How do you use it? And how does it affect your shot of espresso? Join Julia, a technician at Clive Coffee as she shows you how to use the ECM Puristika espresso machine and its new features. 

What is an expansion valve?

The expansion valve in an espresso machine sets and regulates the pressure to the group head. It diverts any excess water based on the set pressure back into the water reservoir.  Typically located on the inside of the machine, expansion valves were not so easily accessible until now.

How does pressure effect my shot of espresso?

Brewing coffee under pressure is what makes espresso — espresso. The industry standard is to brew espresso using 9 bars of atmospheric pressure. A bar of pressure is about 14 psi (so this is a lot of pressure!). On the Puristika, you can adjust the expansion valve between 8 and 12 bar.

Why do I need to adjust pressure?

Typically, you’d make adjustments to an expansion valve as the machine ages or to mitigate coffee or grinder issues. The amount of pressure you use changes your extraction. You should change the pressure, raising it to extract more or lowering it to extract less. Baristas use changes in pressure to pull different flavors from coffee. Adjustments on an expansion valve shouldn’t be confused with pressure profiling which is when you change the pressure at the pump while pulling a shot. Machines that are able to do this, like the GS3 MP and a Slayer, for example, have pressure profiling devices or different pump types.  An expansion valve isn’t intended to be a part of the everyday workflow but can be a good tool for experimenting. 

Some advice on adjusting pressure. 

In a perfect world or for a perfect shot, the pressure gauge will read about 9 bar when a backflush disk is in the portafilter. This confirms that the pump, in combination with the expansion valve is producing 9 bars of pressure and functioning properly. When it comes time to pull a shot and your coffee is too old, too coarse, or your dose is too low, your pressure at the group, reflected on the gauge, may drop. An expansion valve isn't meant to be used to resolve issues with old coffee or a grinder that isn't able to produce grinds fine enough to build pressure at the group head. 

How do I use the adjustment knob?

When you’re ready to make an adjustment to the pressure using the adjustment knob, place the blank basket into your portafilter and insert it into your group head. Lift the brew lever to engage the pump, then slowly move the knob clockwise to raise the pressure and counter-clockwise to lower it. Once you reach your desired pressure, displayed on the gauge, lower the brew lever.

There are other variables to play with that impact coffee extraction, such as brew temperature that can be adjusted through the PID and your espresso recipe. If you have any questions about the ECM Purstika, expansion valves, and pressure profiling, leave your questions below or email us at hello@clivecoffee.com