Espresso channelling
Water blasts through one path in the coffee puck instead of flowing evenly, often visible as an uneven, spurting or fast-then-slow stream.
Applies to: Espresso machine, Espresso
Likely causes and adjustments
Try one adjustment at a time so you know what actually changed the result. Start with the first cause below — if it doesn't help, reveal the next.
Cause 1 of 3 · Reported, not independently verified
Uneven distribution of grounds in the basket before tamping
Distribute grounds evenly across the basket before tamping, using a distribution tool or careful technique.
Related issues
What to change
Specific adjustments for this symptom, with what each one trades off.
Work it out
Interactive tools that take you through this one change at a time.
Learn the technique
Step-by-step guides to the skills this problem comes from.
- Distributing espresso grounds (WDT)Leave the coffee bed uniformly dense throughout, so water meets the same resistance everywhere and does not carve a channel.
- Tamping espressoCompress the coffee bed into a level, uniformly dense puck, without introducing a slope or a crack.
- Diagnosing a shot with a bottomless portafilterRead what the underside of the basket is doing during extraction, and match what you see to the preparation fault that caused it.