This may be helpful for Silvia owners undecided about whether to perform the mysterious ritual of backflushing. Rancilio does not recommend backflushing. But the following is why we tend to ignore that advice and do it regardless.
Whether the Rancilio company likes it or not, their machines "backflush" everytime a shot is pulled. As do all coffee machines with 3-way valves.
The electrically-operatede three-way valve opens to release pressure from the sealed basket through the valve. Othertwise, when the portaflter is unscrewed, there would be a messy explosion of the hot puck all over the kitchen (and barista)
Of course, along with the pressure, are flushed coffee grounds and oils from the puck. Witness the murky dark brown scum in the drip tray.
The valve is a piston-plunger arrangement operated by a solenoid. It closes or opens to direct water.
You can imagine that these get very hot, and after time will consolidate all the gunk inside into a mess which may intefere with the free movement of the piston.
Backflushing with clean water will remove most of the solids. While the less frequent backflush with chemical cleaner will remove oil remnants.
Backflushing with a blind filter will place pressure on the vibe pump. For up to 5 seconds at a time. But only at 9 bars, and the pump is built to take 15 bars.
During those 1-5 seconds, water is returned NOT to the boiler, but back into the water tank. When the brew switch is hit again to stop the pump, the 3-way valve releases water from the group down the valve and into the tray.
When backflushing, I think its worthwhile to first to the wiggle to remove grouds from the sides and sealing surface.
Then do one backflush, remove the sportafilter and empty the blind basket which may well be full of grounds. Then continue so only clean water is forced down the valve.
--Robusto
Whether the Rancilio company likes it or not, their machines "backflush" everytime a shot is pulled. As do all coffee machines with 3-way valves.
The electrically-operatede three-way valve opens to release pressure from the sealed basket through the valve. Othertwise, when the portaflter is unscrewed, there would be a messy explosion of the hot puck all over the kitchen (and barista)
Of course, along with the pressure, are flushed coffee grounds and oils from the puck. Witness the murky dark brown scum in the drip tray.
The valve is a piston-plunger arrangement operated by a solenoid. It closes or opens to direct water.
You can imagine that these get very hot, and after time will consolidate all the gunk inside into a mess which may intefere with the free movement of the piston.
Backflushing with clean water will remove most of the solids. While the less frequent backflush with chemical cleaner will remove oil remnants.
Backflushing with a blind filter will place pressure on the vibe pump. For up to 5 seconds at a time. But only at 9 bars, and the pump is built to take 15 bars.
During those 1-5 seconds, water is returned NOT to the boiler, but back into the water tank. When the brew switch is hit again to stop the pump, the 3-way valve releases water from the group down the valve and into the tray.
When backflushing, I think its worthwhile to first to the wiggle to remove grouds from the sides and sealing surface.
Then do one backflush, remove the sportafilter and empty the blind basket which may well be full of grounds. Then continue so only clean water is forced down the valve.
--Robusto





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