Watery espresso is a concentration problem, and concentration is set by the ratio rather than the grind.
The likely causes
The yield ran too long. Pulling 50 g from an 18 g dose gives a thin drink no matter how well it extracted. Weigh the output and stop at around twice the dose.
The dose was too low. Under-filling a basket means less coffee for the same water.
A pressurised basket. These aerate the output, so the drink looks voluminous while containing less dissolved coffee than it appears to.
Very fresh beans. Coffee under four days old is full of CO₂, which repels water and makes shots run fast and thin. Rest it a few more days.
Watery is not the same as sour
Worth separating. A sour shot is under-extracted and needs a finer grind. A watery shot may be perfectly extracted and simply too dilute — the fix is a tighter ratio, not a grind change.
If it is both, fix the grind first.
The check
Weigh the dose and the yield for three shots. If the ratio is around 1:2 and the drink still tastes thin, the beans or the basket are the problem rather than your technique.
Last reviewed 8 August 2026