Short answer: too fast means the grind is too coarse, the dose too low or the puck is channelling. Too slow means the grind is too fine, the dose too high or the shower screen and basket need cleaning.
Short answer: a shot that runs too fast is almost always too coarse a grind, too low a dose, or channelling through an uneven puck. A shot that chokes is too fine a grind, too high a dose, or a blocked basket and shower screen. Work through those in that order.
Channelling is the one people miss. If the shot starts fast, sprays sideways or pours pale on one side, water is finding a path through the puck rather than passing evenly. Level and distribute before tamping, tamp flat, and stop knocking the portafilter after tamping.
If the grind adjustment no longer does what it used to, suspect the burrs. Commercial burr sets wear out, and worn burrs produce a wide particle spread that pours fast and tastes thin at every setting.
Humidity and bean freshness both move grind settings day to day. Expect to adjust the grinder in the morning and again if the room warms up; that is normal, not a fault.
As a working reference, 25 to 30 seconds for a double of around 36g from 18g in. Different blends will sit either side of that.
Usually a blocked shower screen, a worn gasket or an unequal dose. Swap baskets between groups to confirm which part is at fault.
By kilos ground rather than time. High volume sites wear a set out far faster than a low volume office, so track the weight you put through.
Sometimes. Some blends are far more forgiving of dose and grind variation, which matters on sites without trained baristas. We can suggest a more tolerant profile.
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