5 things that help with espresso that squirts sideways and sprays from a bottomless portafilter

Most people who've heard of WDT do it after mounding grounds into the portafilter. By then you're pushing a compacted dome around — the clumps that cause diagonal sprays are already baked in. They form during dosing, not after. The needle can only do its job while the grounds are still loose enough for it to reach the base of the basket. A shot that squirts to the 3 o'clock position consistently has a channel in exactly that quadrant, and that channel was there before you ever picked up the tamp.

A 58mm basket does not necessarily want a 58mm tamper. The tamper that shipped with your machine almost certainly has a gap of 0.3–0.5mm around the edge when seated. That gap is not cosmetic — the grounds that fall into it receive zero tamping pressure and form a loose, low-resistance ring around the perimeter of the puck. Water wicks straight down that ring and sprays outward in a halo from the basket edge. The textbook 'donut' spray pattern is this problem and nothing else.

The most counterintuitive cause of sideways spray is a grind that is simply too coarse. Beginners almost always assume spray means the puck is too dense or the pressure too high and loosen the grind to fix it — which makes everything worse. A coarse grind gives water large, interconnected passages to accelerate through, and those passages become violent jets when they exit the bottomless basket. The puck barely resists, the water never spreads, and you get a fireworks display. If your shot runs faster than 25 seconds for a 1:2 ratio, the grind is almost certainly the primary cause of the spray.

Some spray that looks like a distribution problem is actually caused by what happens after the puck is made: the group head releases a jet of high-pressure water that strikes the centre of the puck with enough force to physically crater the grounds before extraction has even started. A metal puck screen — a thin perforated disc sitting on top of the coffee — distributes that initial water blast across the full face of the puck, preventing crater formation and giving the water nowhere particular to concentrate. On a bottomless portafilter the effect is immediate: the shot develops as a single cone rather than a fan of jets.

This is the fix nobody wants to hear because it costs money. A basket used daily for two-plus years has worn holes. The micro-perforations — typically 0.35mm in a precise grid — can be enlarged, distorted, or partially blocked by limescale in ways that disrupt water distribution across the puck base before any preparation decision you make even matters. IMS and VST precision baskets have a reputation for consistency largely because their tighter hole tolerances hold longer. But even they wear. The stock basket that shipped with your mid-range machine is usually the first culprit when everything else checks out.