The two parts that wear out on a schedule

Two consumable parts sit at the business end of every espresso machine. Both are cheap, both are replaceable at the kitchen table, and both are routinely left in place for years until they cause a fault that looks much worse than it is.

The group gasket

The gasket is the rubber ring the portafilter seals against. Heat cycles harden it. Once it is hard, it stops deforming to fill the gap, and water finds its way out around the rim instead of through the coffee.

Symptoms, in the order they usually appear:

• The portafilter handle sits further round than it used to. This is the earliest sign and the easiest to miss, because it happens over months. Note where the handle points on a new gasket — that is your reference.
• Water drips or squirts from the edge of the portafilter during a shot.
• The portafilter becomes hard to insert or remove, because the hardened gasket grips.
• Shots run inconsistently, because pressure is leaking rather than pushing through the puck.

Interval: roughly 9–12 months of daily use. Heavier use, sooner. A gasket that has gone hard will look fine — hardness is not visible — so go by time and by handle position, not by appearance.

Sizing: gaskets are specified by diameter and thickness, and the thickness matters as much as the diameter. Fitting a thicker gasket is a known trick to correct a handle that sits too far round, but it changes how far the basket sits from the screen, so it is a correction, not an upgrade. Buy the size your group takes.

Fitting: a hardened gasket usually needs a small screwdriver or a purpose-made hook to lever out, and it will resist. Take the shower screen off first, work around the edge rather than levering from one point, and be careful not to score the seat. The new one goes in with the flat side up on most groups; press it home evenly all the way round.

The shower screen

The screen spreads water across the puck. It is a disc with many small holes, and coffee fines fill those holes from below while oil coats them from above.

Symptoms:

• Water comes out of the group unevenly when you run it with no portafilter — you can see this directly, and it is the single most useful diagnostic on the machine.
• Shots channel repeatedly despite good distribution and a good tamp.
• The underside of the screen stays dark after cleaning.

Interval: clean weekly, inspect quarterly, replace roughly yearly. Screens are cheap enough that replacing one a year is not worth debating.

Sizing: screens are specified by diameter and by the group they fit. Some are held by a central screw, some are a push fit, and some sit under a dispersion block. Take the old one out before ordering so you know which.

Why these get misdiagnosed

Both failures present as pressure and flow problems, and pressure and flow problems get blamed on pumps, valves and grinders — all of which are more expensive to address.

The sequence that saves money: if shots have become inconsistent, run the group with no portafilter and watch the spray pattern. If it is uneven, clean the screen; if cleaning does not fix it, replace it. Then check the handle position against where it used to sit. Only after both of those is it worth suspecting anything electrical or mechanical.

The cost asymmetry

A gasket and a screen together cost a fraction of one service visit. Left in place, they cause leaks that soak the machine's underside, which is how water reaches things that genuinely are expensive. This is the clearest example on an espresso machine of a small scheduled part protecting a large unscheduled bill.

Spare parts are a substantial part of what the retailers we track actually stock — machine-specific spares are their own section of our index, because a gasket for one group is never a gasket for another.