Why Do Espresso Machines Explode & How To Prevent It

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I have been an espresso lover all my adult life and I have often wondered if espresso machines are dangerous or worse – can they explode? 

The process of making an espresso is actually very delicate and complex. Hot water is forcibly pushed through the coffee grounds at high pressure, and the espresso drips out the bottom of the portafilter, ready to be used for the desired drink.

Key Takeaways:

Can an espresso machine explode?

Espresso machines are basically a pressure system with a steam boiler and a pressure relief valve. A malfunctioning steam boiler may produce excessive pressurized steam or a faulty pressure relief valve might not let the steam escape to release the built up pressure. In either of the cases an espresso machine is at the risk of exploding. 

Further explanations for espresso machine explosions

A good espresso machine is a complicated pressure setup whether it’s from De’longhi, Jura, Gaggia or Mr. Coffee. Espresso extraction is highly susceptible to changes in pressure and flow of water. The flow rate of water through the puck dictates your contact time and therefore is proportional to your extraction percentage. 

And pressure is what makes espresso espresso: a thick, quick-to-prepare coffee topped with a colloid of coffee and oils that we call crema. 

The fine grind and hard tamping creates a puck that’s hard for water to get through, which is the whole reason pressure can build up to extract the oils out of espresso. 

Almost all espresso machines pull shots at the commercial standard of 9 bars. To gain some perspective on this, think about pumping up your car or bicycle tire. Most car tires specify that you should pump them up to 32 PSI, pounds per square inch, while on bicycles it might go as high as 65–85 PSI.

9 bars, however, is the equivalent of 130 PSI – over four times as much as a car tire. If heat is continuously supplied to the steam boiler, it will keep producing and holding steam under high-pressure. If this kind of pressure keeps getting accumulated and is not allowed to break free either through the tap, milk frother or the steam relief valve, the steam boiler will eventually end up exploding.

Check out our list of the best small espresso machines and pod espresso machines.

How to prevent espresso machines from exploding

As we discussed before – an espresso machine is a complicated pressure system of boilers, valves, pipes, reservoir and many other essential parts. Depending on the model, espresso machines have a lifespan of 8–10 years, as long as you take good care of them. Here are a few steps that you can take to prevent your machine from malfunctioning and causing any harm to you.

Get into the habit of cleaning your machine properly every day:
  • Do a full backflush: scrub the group heads with a machine brush to loosen and remove coffee grounds.
  • Clean the steam wand
  • Clean the draining hose
  • Make sure to clean the portafilters, filter basket, and drip tray.
A minor service of your espresso machine every three months:
  • Replace group gaskets.
  • Replace shower screens
  • Test group flow rates and temp.
  • Test all switches.
  • Test grouphead and boiler water quality
An annual service of your espresso machine:
  • Replace your pressure safety valve.
  • Replace your portafilter baskets.
  • Replace the waste pipe (if needed).
  • Replace the capacitor on the pump motor and before solenoids.
  • Replace the sight glass.
  • Replace or servicing your non return valve.
  • Check for steam or water leaks.

Are espresso machines dangerous?

If not maintained properly, an espresso machine can be a dangerous appliance. There is boiling water, pressurized steam, and above all, electricity to contend with.

It can burn you

Espresso machines boil water to produce steam that is held at very high pressure inside the boiler. Most parts of the machine such as the portafilter, steaming wand are made up of stainless steel or other metals which can get very hot. You may get burnt if you don’t exercise proper care while or after making an espresso, since that is the time when machine parts are the hottest.

Steam/water leak

Steam boiler or water reservoir seals might get worn out causing it to leak which may damage your countertop or other nearby kept appliances. Hot steam may harm the plastic components of your other kitchen appliances and may rust the metal parts and fixtures.

Breeding ground for germs

Espresso machines, if not cleaned properly can be a hot spot of food borne illnesses. A faulty machine might not reach the optimum temperature for killing bacteria in the steaming wand, and may end up serving an espresso which may cause food poisoning. 

Is it OK to leave espresso machine on

Modern espresso machines heat up quickly so it doesn’t make sense to keep them on all the time. Moreover, keeping the machine on and heated all the time not just wastes electricity but it also reduces the lifetime of gaskets, screen and electrical parts like signal lights, solid state relays, control boxes, solenoid valves, and motors.

Written by:
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Amit Gupta

Hi, my name is Amit Gupta, and I am the owner and contributor at Cafeish. My obsession with coffee started when I received my first French press as a gift almost ten years ago. Since then, my love of coffee – and the number of coffee gadgets I own – has grown considerably.

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