Most espresso machine owners clean their machines far less often than they should — and their coffee pays the price. The problem is that coffee oil build-up happens so gradually that you might not even notice how much your espresso has deteriorated until you clean the machine and taste the difference.
In this guide we'll cover the 5 most common warning signs that your espresso machine urgently needs cleaning, what causes each problem, and exactly how to fix it.
This is the most obvious and most common warning sign. If your espresso has developed a harsh, bitter or unpleasant aftertaste that wasn't there when you first got your machine, rancid coffee oil build-up is almost certainly the cause.
Here's what happens: every time you pull an espresso shot, coffee oils from the grounds are left behind in the group head, shower screen and portafilter. These oils oxidise over time and go rancid — just like cooking oil that has been left out for too long. When you pull your next shot, hot water passes through this rancid residue and carries it into your cup.
The result is espresso that tastes stale, harsh and bitter — no matter how good your coffee beans are or how perfectly you've dialled in your grind and dose. Many home baristas blame their beans or their grinder when the real culprit is a dirty machine.
⚠ A single backflush with a cleaning tablet can restore your espresso's flavour immediately. The difference in taste after cleaning a neglected machine is often dramatic.
The fix: Backflush with one Qualità Napoli cleaning tablet. The tablet dissolves completely, carrying all rancid coffee oils and residue out of the group head. Pull a test shot after cleaning — you should immediately notice a cleaner, more balanced flavour.
Take a look at your machine's group head — the part that the portafilter locks into. Look carefully at the shower screen (the metal disc with small holes that water passes through) and the rubber seal around the edge of the group head.
If you can see a dark brown or black film of residue around the group head, shower screen or on the inner walls of the portafilter basket, your machine is well overdue a clean. This dark residue is compacted coffee oil and fine grounds that have baked onto the metal surfaces with repeated heating.
This residue will continue to contaminate every shot you pull until it is properly removed. Simply rinsing with water is not enough — only a backflush with an espresso cleaning tablet will properly dissolve and remove baked-on coffee oil residue.
The fix: Backflush with a cleaning tablet and also remove the shower screen if possible to soak it separately in hot water with a cleaning tablet for 20-30 minutes. Use a group head brush to scrub away any remaining residue.
A properly functioning espresso machine should produce a steady, consistent flow of espresso during extraction. A shot typically takes 25-30 seconds to extract 36ml of espresso from a double basket with 18g of coffee.
If your espresso is taking significantly longer to extract than usual, or if the flow seems inconsistent — spurting, dripping unevenly, or coming out in an uneven pattern — this strongly suggests that the shower screen or internal three-way valve is partially blocked with coffee residue.
A blocked shower screen affects water distribution across the coffee puck, leading to uneven extraction. Some parts of the puck receive too much water while others receive too little — resulting in a shot that is simultaneously over-extracted (bitter) and under-extracted (sour) in different areas.
A partially blocked valve can also cause pressure inconsistencies that affect espresso quality and can, over time, put additional strain on the machine's pump.
⚠ Don't mistake a slow flow rate for a grind that is too fine. If your grind hasn't changed but the flow has slowed, a dirty machine is the most likely cause.
The fix: Backflush with a cleaning tablet to clear the valve and internal passages. Remove and soak the shower screen separately. If the problem persists after cleaning, the shower screen may need to be replaced — they are inexpensive and widely available.
Many modern espresso machines — including all Sage models (Barista Express, Barista Pro, Barista Touch), most De'Longhi pump machines, and various other brands — have built-in cleaning cycle alert systems.
These alerts are typically triggered by shot count — the machine tracks how many shots have been pulled since the last cleaning cycle and activates the alert when it calculates that cleaning is due. On most machines this happens around every 200 shots.
When this light comes on, your machine is telling you clearly and unambiguously that it needs a clean right now. Do not ignore it or attempt to reset it without running a proper cleaning cycle. Running a machine in this state accelerates internal wear and can cause damage to seals and valves.
On Sage machines: When the cleaning alert activates, insert the blind basket with a cleaning tablet and press and hold the 1-cup and 2-cup buttons simultaneously to start the automated cleaning cycle.
On De'Longhi machines: Refer to your machine's manual for the specific button combination to activate the cleaning cycle. Insert a blind basket with one cleaning tablet before starting.
The fix: Run a full cleaning cycle with one Qualità Napoli tablet as soon as the cleaning alert activates. Do not delay.
This is a warning sign that many home baristas overlook — but it's one of the most reliable indicators of a machine that needs cleaning.
After removing the portafilter from the group head, give it a sniff — both the inside of the basket and the underside of the portafilter handle. If you notice a stale, musty, rancid or strongly "old coffee" smell rather than the fresh roasted coffee scent you'd expect, you have significant oil build-up that needs addressing immediately.
This rancid smell comes from oxidised coffee oils that have accumulated over many shots without being properly cleaned away. These oils are not just unpleasant — they are actively contaminating every shot you pull and making your espresso taste worse.
The fix: A thorough backflush with a cleaning tablet will address the internal machine. Also soak the portafilter and basket in hot water with a cleaning tablet for 30 minutes to dissolve the oil build-up on these parts. After soaking, scrub with a basket brush and rinse thoroughly.
Beyond the five main warning signs above, watch out for these additional indicators that your machine needs attention:
All five of the main warning signs above — and most of the bonus signs — can be resolved with a single espresso machine cleaning tablet and five minutes of your time. Read our complete step by step backflushing guide for full instructions. Here's the quick process:
The best way to avoid all five warning signs is simple — clean your machine regularly before problems develop:
A consistent cleaning routine takes less than 10 minutes per week and will keep your machine producing excellent espresso for years to come.
My espresso tastes bitter — is it my beans or my machine?
If the bitterness developed gradually over time and your beans haven't changed, it's almost certainly your machine. Clean it with a backflush tablet and compare the taste. If the bitterness disappears, the machine was the problem.
How quickly will cleaning improve my espresso taste?
Immediately — the very first shot after a proper backflush cleaning should taste noticeably cleaner and more balanced. The improvement is often dramatic on a machine that hasn't been cleaned for a while.
My cleaning light came on but the machine seems fine — do I still need to clean it?
Yes absolutely. The cleaning alert is based on shot count, not on whether the machine appears to be working. Clean it immediately when the light activates.
Can I use any cleaning tablet or does it matter which one I use?
Always use tablets specifically designed for espresso machine backflushing. Never use dishwasher tablets, household cleaners or descaling tablets for backflushing. Qualità Napoli tablets are specifically formulated for espresso machine cleaning and are food-safe and phosphate-free.
One Qualità Napoli cleaning tablet is all it takes to restore your espresso machine to perfect condition. Compatible with Sage, De'Longhi, Breville, Jura and all major brands. Fast UK delivery from just £8.99.
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