Is it bad to leave the coffee puck inside the espresso machine

Is it Bad to Leave the Coffee Puck Inside the Espresso Machine?

If you’re new to brewing espresso at home, you’ve probably made your first few delicious shots of espresso. And during the clean up, the question has probably crossed your mind if leaving the coffee puck in your espresso machine until your next shot will be harmful.


Leaving the coffee puck inside the portafilter basket of your espresso machine can have negative effects. It can lead to clogging of the espresso machine group head, unpleasant odors and flavors due to bacteria growth, and damage to the machine over time. As a result, it is recommended to remove the coffee puck after each shot and dispose of it correctly.

It’s best to make a habit of removing the coffee puck after each shot and dispose of it properly. In this blog post, we’ll dive deeper into the reasons why leaving the coffee puck inside your espresso machine is not a good idea, and provide tips on how to properly dispose of it after each shot.

Potential Consequences of Leaving the Coffee Puck Inside the Espresso Machine

Leaving the coffee puck inside the espresso machine after brewing can have various consequences that can negatively impact both the machine and the quality of your coffee.

Clogging of the Group Head

One of the immediate consequences of leaving the coffee puck inside the machine is the risk of clogging the group head.

The group head is the part of the machine that comes into contact with the coffee puck during extraction. Below are possible issues that can arise from a clogged group head.

  • Reduced Water Flow and Inconsistent Extraction: As the coffee puck sits inside the group head, it gradually dries out and hardens. Over time, this hardened puck can impede the water flow during the brewing process. The restricted flow prevents water from evenly saturating the coffee grounds, resulting in uneven extraction. Inconsistencies in extraction can lead to flavor imbalances, weak shots, or shots that lack the desirable characteristics of a well-extracted espresso.
  • Back Pressure Buildup and Channeling: Another consequence of a clogged group head is an increase in back pressure. When water encounters resistance due to a partially or fully blocked group head, it seeks alternative paths to escape. This can cause channeling in either your coffee puck itself, or back into your machine.
  • Increased Cleaning and Maintenance Efforts: Leaving the coffee puck inside the group head can also create more work in terms of cleaning and maintenance. The hardened dry puck becomes more challenging to remove, requiring additional effort to dislodge it from the machine. This can prolong the cleaning process and increase the likelihood of damage to the group head or other parts of the machine during puck removal.

When the coffee puck remains in the group head for an extended period, it can dry out, harden, and become difficult to remove.

As a result, your espresso shots may become weak, under-extracted, or inconsistent in flavor.

Health Hazards

Leaving the coffee puck inside the machine can also pose health hazards. Over time, the residual moisture in the coffee puck can create a breeding ground for mold, bacteria, and other microorganisms.

Here are a few health-related concerns that may arise:

  • Mold and Bacterial Growth: When the moist and organic environment of the coffee puck is left undisturbed inside the machine, it becomes a breeding ground for mold and bacteria. Over time, these microorganisms can multiply and contaminate the machine. If not addressed promptly and adequately cleaned, they can pose health risks, especially to individuals who are sensitive or allergic to mold or bacteria.
  • Unpleasant Odors and Tastes: The presence of mold and bacteria can lead to the development of unpleasant odors and tastes in your espresso. These microorganisms can produce compounds that alter the flavor profile of the coffee and create off-notes that are undesirable.
  • Cross-Contamination: If the espresso machine is not cleaned properly and the coffee puck is left inside, there is a risk of cross-contamination of old coffee particles and your fresh ground coffee beens which ultimately can effect the overall flavor profile. Residual coffee oils and coffee particles from previous brews can mix with fresh coffee grounds, resulting in flavor inconsistencies and compromising the quality of the espresso.

Additionally, the buildup of old coffee grounds can attract pests, further compromising hygiene and sanitation. To ensure a safe and clean brewing environment, it is crucial to remove the coffee puck promptly and clean the machine regularly.

Damage to the Machine

Leaving the coffee puck inside the machine can cause damage to its components. The moisture from the coffee puck can seep into sensitive parts, leading to corrosion and deterioration.

The residual oils in the coffee grounds can also accumulate and create a sticky residue, affecting the performance and functionality of the machine.

It’s important to note that the specific damages can vary depending on the machine’s design and construction but over time, this can result in over-all malfunctions, reduced brewing capabilities, and costly repairs or replacements.

Shortened Longevity of the Machine

Proper maintenance and care play a significant role in extending the longevity of your espresso machine.

By leaving the coffee puck inside the machine and neglecting regular cleaning, you expose the machine to unnecessary wear and tear. The accumulation of residue, clogs, and damage from moisture can significantly impact the lifespan of the machine.

By adopting good maintenance practices, such as promptly removing the coffee puck and cleaning the machine after each use, you can ensure its optimal performance and prolong its lifespan.

It is important to note that each espresso machine may have specific instructions and recommendations regarding puck removal and maintenance. Refer to the manufacturer’s guidelines to understand the best practices for your particular machine and incorporate them into your coffee routine.

Can leaving the coffee puck inside the machine also affect the taste of my espresso?

The steps you take after extracting the shot can significantly influence the final taste and quality of your beverage. Leaving the coffee puck inside the machine will have some effect on the taste of your espresso. The old coffee grounds can become stale and rancid, which can lead to unpleasant flavors in your shot.

Let me explain.

Leaving the coffee puck inside the machine can introduce various factors that can alter the taste of your espresso like the prolonged exposure of the leftover coffee grounds to heat and moisture.

Over time, this can lead to the development of off-flavors and undesirable aromas in the coffee puck, which can then transfer to subsequent shots. The residual oils and compounds present in the used coffee grounds can turn rancid, resulting in a stale and unpleasant taste.

But it doesn’t stop there. Leaving the coffee grounds inside the machine can contribute to the buildup of residue and bacteria. This can result in mold growth or other forms of contamination, which can further degrade the flavor and quality of your espresso.

Additionally, the residual moisture from the coffee puck can cause clogging and blockages within the machine’s brewing components, affecting water flow and extraction consistency. This can lead to under-extraction or over-extraction, resulting in imbalanced flavors and a subpar espresso experience.

What’s the best way to dispose of the used coffee puck after each shot?

With all that being said, how should you go about disposing of the coffee puck in the portafilter basket after making your delicious shot of espresso?

The best way to dispose of the used wet coffee puck is by removing it from the portafilter basket and discarding it in an appropriate manner immediately after use.

You can tap the portafilter gently to release the puck into a container like a knock box. If you’re not familiar with what a knock box is, a knock box is a specialized container designed for the convenient disposal of coffee pucks.

These are great because they provide a designated space for knocking out the used coffee puck from the portafilter, eliminating the need to tap it against other surfaces or create a mess.

From there you can easily toss the collection of coffee grounds into the garbage, compost bin, or appropriate container depending on your location’s disposal specifications.

Beyond simple disposal, used coffee grounds can find new life in various alternative uses like garden fertilizer for instance.


Removing the coffee puck from your espresso machine after each shot is essential for maintaining the functionality and longevity of the machine. Leaving the puck inside the machine can lead to clogging, health hazards, and damage to the internal components. Additionally, it can affect the taste of your espresso, leading to unpleasant flavors and other negative effects. By properly disposing of the coffee puck and regularly cleaning and maintaining your machine, you can ensure it stays in top condition and continues to produce delicious shots of espresso.