A blind — or blank — basket is a filter basket with no holes. Water cannot get out through the bottom, so when the pump runs it has nowhere to go but backwards.
What it does
Fitting it and running the pump forces water up through the shower screen and back through the group head, flushing out the coffee oils that accumulate above the screen where normal brewing never reaches.
With a cleaning tablet in the basket, that becomes a detergent cycle.
It only works with a three-way solenoid
This is the crucial requirement. The water pushed backwards has to escape somewhere, and on machines with a three-way solenoid it goes out through the drain into the drip tray.
On a machine without one, backflushing does nothing and can damage the pump, because there is nowhere for the pressure to go. Most thermoblock machines — the Dedica, the Bambino, most bean-to-cup units — cannot be backflushed.
Check your manual before trying.
How to use it
Blind basket in, tablet on top, lock in. Run the pump for ten seconds, stop for ten, repeat five times. Then remove the tablet and repeat with water only, several times, until the water runs clear.
How often
With water after every session. With a tablet weekly for heavy use, monthly otherwise.
Last reviewed 8 August 2026