Slow Espresso Shots: Diagnosis Order

Step 1: Verify the measurement

• Was the yield weighed?
• Was the timer started at pump on or first drop, and is that consistent with your log?
• Did the shot stall and then catch up, or was it slow throughout?
• Was the cup tared properly?

A shot that takes 40 seconds to reach 40 g is slow. A shot that takes 40 seconds to reach 25 g is slow *and* under-yielded, which is a different problem. Record both.

Step 2: Check dose and basket fit

An overfilled basket is a common cause of slow, erratic flow. If the puck touches the shower screen, it can compress, deform, and restrict water. Check:

• Does the screen leave an imprint in the puck?
• Does locking in feel tight?
• Is the dose at the top of the basket's practical range?
• Did you change coffee to a denser bean at the same dose?

If the basket is overfilled, reduce dose slightly before touching the grind. This is often the fastest fix and is easy to miss.

Step 3: Look at the puck and flow

• Even slow flow: likely grind or dose.
• Slow start, then a sudden gush: channeling after a partial seal.
• Barely any flow, then a spurt: blockage or severe channeling.
• Slow throughout with a soupy puck: underfilled or a grind that is far too fine.

A puck that comes out in a solid, wet cake can indicate too fine a grind or too much coffee. A puck with a hole indicates channeling.

Step 4: Grind coarser by one step

If dose and basket fit are sane, grind coarser by one small step. Keep dose, yield, and technique constant. Repeat and compare. On stepped grinders, one click may move the shot a lot; note the change.

Do not jump several steps. If you overshoot into a fast, thin shot, you have lost the reference point and will spend the next three shots returning to it.

Step 5: Check distribution and tamp

A puck that is dense on one side and loose on the other can slow flow while still channeling. If the shot is slow and the taste is harsh, suspect uneven prep rather than a uniformly fine grind. Level the bed, check the tamp is square, and try again at the same setting before changing grind.

Step 6: Consider the coffee

Very fresh coffee can behave erratically, sometimes slow, sometimes fast. A dark roast can also produce more fines and slow flow at a given setting. Note roast date and roast level. If the coffee is new, give it a few days and keep the recipe stable.

Step 7: Check the machine

Machine-side causes are less common but real:

• A clogged or partially blocked shower screen.
• A basket with damaged or blocked holes.
• A flow restriction or scale build-up, depending on the machine and water.
• A pump or valve issue.

These usually affect every coffee and basket, not one shot. If the slow behaviour follows the machine rather than the coffee, investigate. Follow the manufacturer's guidance for cleaning and service; do not disassemble beyond what is documented.

Decision table

What to log

Bottom line

Verify the measurement, check basket fit, read the puck, then go coarser by one step. Rule out channeling and coffee before blaming the machine. Change one variable per shot and record it, so a slow shot becomes information rather than a mystery.