Every home barista has experienced it: the frustration of pulling shot after shot that just doesn't taste right. Perhaps it gushes through in fifteen seconds and tastes like sour lemon water. Maybe it drips out slowly and bites with harsh bitterness. Espresso is unforgiving—small errors in any variable compound into noticeable flaws in the cup. But with systematic troubleshooting, you can diagnose and fix almost any issue. This guide walks through the most common espresso problems and their solutions.
Problem: Shot Runs Too Fast (Under-Extraction)
Your espresso pours quickly—perhaps reaching full volume in under twenty seconds—and tastes thin, sour, and sharp. The crema may be pale and thin, dissipating quickly. This is under-extraction: water passed through the coffee too quickly to extract the good stuff.
Possible Causes and Solutions
- Grind too coarse: This is the most common culprit. Finer your grind incrementally until the shot slows to the 25-30 second range.
- Insufficient dose: If there's not enough coffee in the basket, water has less resistance. Weigh your dose and ensure it matches the basket capacity (typically 18-20g for a double).
- Poor distribution: If coffee is unevenly distributed in the basket, water finds the path of least resistance and channels through quickly. Use a distribution tool or WDT technique.
- Inadequate tamp: A light or uneven tamp leaves gaps for water to rush through. Apply firm, level pressure.
- Stale coffee: Beans past their prime produce less crema and extract poorly. Use coffee within two to four weeks of roast date.
Target extraction time for espresso is typically 25-30 seconds for 30-40ml of liquid from an 18-20g dose. Times vary with recipe and preference, but this range is a solid starting point. Adjust grind size as your primary control variable.
Problem: Shot Runs Too Slow (Over-Extraction)
The espresso drips out painfully slowly or barely at all. What finally appears in your cup tastes bitter, harsh, and astringent, with an unpleasant drying sensation on your tongue. This is over-extraction: water spent too long in contact with the coffee, pulling out undesirable compounds.
Possible Causes and Solutions
- Grind too fine: Coarsen your grind incrementally. Very small adjustments make significant differences at the fine end of the spectrum.
- Overdosing: Too much coffee creates excessive resistance. Weigh your dose and reduce if above basket capacity.
- Excessive tamping: While firm tamping is good, excessive force compacts the puck too densely. Aim for consistent, moderate pressure—about 15kg of force.
- Blocked shower screen: Coffee residue can clog the screen's holes, restricting water flow. Remove and clean the screen regularly.
- Machine at fault: If pump pressure is too high, the machine may be forcing water through too slowly. This requires professional adjustment.
Problem: Channelling
Channelling occurs when water finds a weak spot in the coffee puck and rushes through it, leaving other areas under-extracted. You might see the espresso spraying from specific points on the basket bottom, or the stream may appear uneven—blonde on one side, darker on the other. The resulting shot is simultaneously sour and bitter, combining the worst of both under- and over-extraction.
Possible Causes and Solutions
- Poor distribution: Before tamping, ensure grounds are evenly distributed. A WDT tool (essentially a fine needle) stirred through the grounds breaks up clumps and creates even density.
- Uneven tamp: If you tamp at an angle, one side compacts more than the other. Practice tamping with your elbow above the portafilter, pressing straight down.
- Cracks in the puck: Knocking or jarring the portafilter after tamping can crack the puck. Handle it gently.
- Edge channelling: If water runs down the sides between the puck and basket, the puck may be too small for the basket. Increase your dose slightly or ensure you're tamping fully to the edges.
- Worn gasket: A degraded group head gasket can allow water to bypass the puck. Inspect and replace if needed.
Weiss Distribution Technique involves using a thin needle or specialised tool to stir through the grounds in your portafilter before tamping. This breaks up clumps from the grinder and creates uniform density throughout the puck. It's one of the most effective ways to combat channelling and costs almost nothing to implement.
Problem: Weak or No Crema
Good crema—the golden-brown foam layer atop espresso—indicates proper extraction and fresh coffee. If your shots lack crema, or it appears thin and disappears quickly, something's off.
Possible Causes and Solutions
- Stale coffee: Crema comes from CO2 trapped in fresh-roasted beans. Coffee past its prime has degassed and won't produce much crema. Use beans within 7-21 days of roasting.
- Under-extraction: Shots that run too fast don't develop proper crema. Dial in your grind as described above.
- Low pressure: Espresso machines need approximately 9 bars of pressure for optimal extraction. Some budget machines don't achieve this consistently.
- Water temperature too low: Insufficient heat affects extraction and crema development. Ensure your machine is fully heated before pulling shots.
- Oily beans: Very dark roasts have oils on the surface that can interfere with crema formation. Try a lighter roast.
Problem: Bitter Espresso
Bitterness is distinct from the pleasant intensity of good espresso. Problematic bitterness tastes harsh, burnt, and lingers unpleasantly. It often comes with a dry, astringent mouthfeel.
Possible Causes and Solutions
- Over-extraction: The most common cause. Shorten extraction by coarsening grind or reducing dose.
- Water too hot: Excessive temperature scorches coffee. If your machine allows temperature adjustment, try reducing by a few degrees. Standard brewing temperature is 92-96°C.
- Dark roast: Very dark roasts are inherently more bitter. Try a medium roast.
- Dirty equipment: Rancid coffee oils buildup on group heads, portafilters, and shower screens contributes bitterness. Clean your equipment regularly.
- Old coffee: Paradoxically, while stale coffee under-extracts easily, it can also produce bitter, papery notes. Use fresh beans.
If your espresso develops a lingering bitter or rancid taste despite fresh beans and good technique, dirty equipment is likely the cause. Backflush with cleaner weekly, clean the shower screen regularly, and don't neglect the portafilter basket and spouts.
Problem: Sour Espresso
Sour espresso has an unpleasant acidic bite, like underripe fruit or vinegar. It's often thin-bodied and lacks sweetness. This indicates under-extraction—the sugars and balancing compounds didn't make it into your cup.
Possible Causes and Solutions
- Under-extraction: Grind finer to slow the shot and extract more solubles.
- Water too cool: Insufficient temperature doesn't extract properly. Allow extra heating time or adjust temperature settings if available.
- Dose too low: Increase your coffee dose slightly.
- Very light roast: Light roasts are naturally more acidic. Try going slightly darker or adjusting extraction to maximise sweetness.
- Pre-ground coffee: Pre-ground coffee stales rapidly and often extracts poorly. Grind fresh for each shot.
Problem: Machine Won't Build Pressure
The pressure gauge barely moves, and espresso pours out weak and fast regardless of grind adjustments. This indicates a mechanical issue rather than a technique problem.
Possible Causes and Solutions
- Scale buildup: Severe scale can restrict water flow through the pump and group head. Descale the machine thoroughly.
- Failing pump: Pumps wear out over time. You may hear unusual sounds or vibrations. Professional repair or replacement is needed.
- Air in the system: Air locks can prevent proper pressure buildup. Run water through the group head and steam wand to purge air.
- Leaking components: Check for water leaking from anywhere other than the group head during extraction. Leaks prevent pressure buildup.
Systematic Troubleshooting Approach
When espresso goes wrong, resist the urge to change multiple variables at once. Instead:
- Identify the symptom: Fast/sour? Slow/bitter? Channelling? No crema?
- Change one variable: Usually grind size first, as it has the most impact.
- Pull another shot: Evaluate the result.
- Iterate: Continue adjusting that variable until the problem resolves or you rule it out.
- Move to the next variable: Dose, distribution, tamp, etc.
Keep notes if helpful. Many baristas log their settings—grind, dose, yield, time—especially when dialling in new beans. This methodical approach prevents chasing your tail and builds understanding of how each variable affects extraction.
When to Seek Help
Some problems require professional intervention. If you've systematically addressed technique and bean freshness but still experience pressure issues, temperature inconsistency, or mechanical noises, your machine may need servicing. Delaying repairs often leads to more extensive (and expensive) damage. A qualified technician can diagnose issues you can't see and restore your machine to proper function.
With patience and systematic troubleshooting, most espresso problems are solvable at home. The process teaches you about extraction and makes you a better barista. Soon, diagnosing and correcting issues becomes second nature, and great espresso becomes the norm rather than the exception.