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Espresso sprays sideways from a bottomless portafilter

One or more jets fire sideways from the underside of the basket during the shot, instead of the flow converging into a single stream.

Applies to: Espresso machine, Espresso

Why a bottomless portafilter sprays

CoffeeHQ explanation

A spouted portafilter collects everything that leaves the basket and hides how it left. A bottomless one shows you the underside of the basket directly, so a fault that was always there becomes visible, and messy. A spray is a jet: water has found a path through the puck that is much easier than the rest and is leaving through a few holes at high speed, while the neighbouring holes drip or do nothing.

That path is a channel. It forms where the bed is less dense, most often along a clump that never broke up, down the wall of the basket where the tamper did not reach, or through a crack opened when the portafilter was knocked after tamping. The portafilter has not caused any of this. It has reported it.

Causes, most likely first

There are 4 likely causes, listed with the most probable first. Work down the list and change one thing at a time, so that when the problem goes away you know which change fixed it.

  1. Cause 1 of 4 · Commonly the cause

    Channelling from clumped or unevenly distributed grounds

    What to change
    Stir the dose with a fine-needle tool before levelling and tamping.

  2. Cause 2 of 4 · Commonly the cause

    Tamp not level

    How to check
    Is the jet coming from one side rather than the centre?
    What to change
    Tamp with the portafilter resting on a flat surface, watching that the tamper stays horizontal.

  3. Cause 3 of 4 · Reported, not independently verified

    Tamper undersized for the basket, leaving an uncompressed ring at the wall

    What to change
    Measure the basket's internal diameter and match the tamper to it.

  4. Cause 4 of 4 · Reported, not independently verified

    Dose too large for the basket, so the puck is crushed against the shower screen

    What to change
    Reduce the dose until there is clear headroom above the tamped puck.

If none of these fixes it

Check the cleaning and descaling guide. Equipment that needs maintenance can cause several of these symptoms at once, and no change of recipe will correct it.

Work through it for your setup

The causes above are general. These go to the part of a diagnostic that takes this symptom one check and one change at a time.

  1. Make my coffee better: Espresso machineEvery reading for this brewer: the check, and the one thing to change first
  2. Espresso puck preparation: the sequence

Fix the bed before the grind

Look at where the jet comes from. A spray from the edge points to the rim of the puck: a tamper that is too small for the basket, or grounds piled in the middle and never spread. A spray from the middle points to clumps or to a dose so large the puck is touching the screen. Then change the preparation, not the setting: stir through the full depth of the grounds with fine needles, level the surface, tamp once and square, and lock in without knocking the handle.

Grinding finer is the instinct and usually makes it worse. A finer grind raises the pressure across the puck, and a bed with a weak spot gives way sooner under more pressure.

A few stray drops are not a fault

The first second of almost any shot shows uneven beading before the streams merge, and one or two fine sprays at the very start are common even from well-prepared pucks. Very fresh coffee, still full of gas, also spits. Judge by what happens after the first few seconds: if the flow gathers into a single stream and the cup tastes balanced, there is nothing to fix.

Easily confused with

  • Channelling you can taste — Spraying is what channelling looks like; sour and harsh together is what it tastes like. You can have the taste without the spray, on a spouted portafilter, and the cause is the same.
  • A sloped tamp — A sloped tamp makes one whole side of the basket flow first and pale early, in a broad sheet. A channel makes a thin, fast jet from one spot.

What not to change at the same time

Do not adjust the grind while you are changing how you distribute and tamp. Until the flow is even, shot time tells you nothing reliable about the grind.

How to tell it is fixed

Beads appear across the whole underside of the basket within a second or two of each other, merge towards the centre and fall as one steady stream that pales gradually.

If that changed nothing

If careful preparation still gives a jet from the same place every time, turn the basket a quarter turn in the portafilter. A jet that moves with the basket is a damaged or blocked hole; one that stays put is the shower screen delivering water unevenly and needs cleaning.

Espresso dial-in assistant — Enter the shot with 'sprayed or flowed unevenly' as what you saw. The assistant puts evenness ahead of grind and tells you what to hold constant while you fix it.

Related issues

Learn the technique

Step-by-step guides to the skills this problem comes from.

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