Technical guide
Shower screen and backflushing: cleaning the brew group step by step
Backflushing cleans the inside of the brew group: a blind basket with espresso machine detergent is locked in and the pump is run in short cycles, then everything is rinsed with clean water. The shower screen is cleaned every day, soaked in detergent solution when residue builds up and replaced when it is dented or blocked.
What is backflushing and which machines can be backflushed?
It means running the pump against a blind basket (one with no holes), so that water and detergent are pushed back through the group and out through its discharge valve to the drain. It only works on groups with that discharge path: a three-way solenoid valve or, on E61 lever groups, the mechanical bleed valve.
This removes the coffee oils and fines left behind the shower screen and in the valve. A group with no discharge path has nowhere to send the solution and should not be backflushed; many spring-lever groups are in that position. Follow the machine's manual. Blind baskets are in Baskets & Shower Screens.
How do you backflush a group with a blind basket?
The blind basket goes into the portafilter with the detergent dose, the portafilter is locked in, the pump is run for a few seconds, stopped so the group discharges, and the cycle repeated; the same is then done without detergent to rinse.
- With the machine at working temperature, brush the area around the group gasket.
- Put the blind basket in the portafilter and add the detergent dose stated on the pack.
- Lock the portafilter in and run the group for about 10 seconds; stop for 10 seconds; repeat about five times. On machines with an automatic cleaning programme the cycle runs by itself.
- Remove the portafilter and rinse it under the group.
- Repeat the cycles without detergent to rinse.
- With the normal basket refitted, brew one coffee and discard it before going back into service.
How much detergent, how many cycles and how often?
It depends on the machine and the detergent: manuals range from about 3 g to a spoonful per group, and from a daily clean in commercial service to one clean every 90 to 140 cups on a small E61 machine.
| Source | Detergent per group | Cycles | Frequency |
|---|---|---|---|
| Label of a common powder detergent | up to 3 g (half a teaspoon) | 10 s on, 10 s off, 5 times; then 5 times without detergent | — |
| La Marzocco Linea PB manual | one tablespoon | automatic programme (AV); 3 s, 10 times (MP) | — |
| Nuova Simonelli Appia II manual | two spoonfuls of cleanser | 10 s, several times | at least once a day |
| Rancilio Classe 5 manual | as stated on the pack | automatic programme or manual cycle | at least once a day |
| ECM Synchronika II manual (E61) | 3 to 5 g | lever up, then half-way for about 20 s, then down; repeat until the water runs clear | every 90 to 140 cups |
On E61 groups, ECM warns that cleaning with detergent too often degreases the moving parts: the lever starts to squeak and wear speeds up. Between cleans, use water only.
How do you clean the shower screen?
Day to day it is cleaned in place; when residue persists, it is taken off and soaked with its screw in hot detergent solution for about 30 minutes, then rinsed well.
Screens with a centre hole come off by undoing the shower screen screw; on E61-pattern groups the screen is a push fit held by the group gasket. For the soak, the La Marzocco manual gives 2 to 3 teaspoons of detergent in half a litre of boiling water; the detergent label gives 6 g per litre of hot water. Do not use aluminium containers. After refitting, run hot water through the group several times.
Manuals differ on brushing: ECM has both the gasket and the screen brushed, Rancilio has the gasket brushed but not the screen.
When should the shower screen be replaced?
When it is dented, the mesh is torn or holes stay blocked after soaking; on a commercial machine, also at the planned interval. La Marzocco schedules new screens every three to four months, together with the group gaskets.
A damaged screen spreads water unevenly over the coffee and extraction becomes irregular. When ordering, confirm the diameter, the fixing (push fit, or centre hole and its screw) and the shape, flat or concave. The shower screen holder and the screw are separate parts and, like the screens, are found in Baskets & Shower Screens.
FAQ
- Can I backflush with water only?
- Yes. A water-only backflush between detergent cleans flushes out loose coffee without stripping the lubrication. The ECM manual recommends cleaning the E61 group without detergent from time to time for that reason. It does not replace the detergent clean, which is what dissolves the coffee oils.
- Is a blind basket the same as a blind disc?
- They do the same job. A blind basket is a filter basket with no holes; a blind disc sits inside a normal basket and closes it off. Choose by portafilter diameter: 58 mm on most groups and brand-specific sizes on makes such as La Spaziale, La San Marco or Dalla Corte.
- Why does the coffee taste of detergent after cleaning?
- Because the rinse was too short. Repeat the cycles without detergent, run water through the group and brew one coffee to throw away before serving, as the detergent label and the manuals instruct.
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