Updated for 2021.
Backflush. What a funny combination of words. For the new espresso machine user this obscure play on words has been one of the great mysteries of the espresso world. This tech tip will give you the inside scoop on backflushing without having to go through the pains of asking.
Backflushing is the process used to clean out the shower screen, brew group and three-way valve. Backflushing can only be done with machines that have a three-way valve. The three-way valve is a small valve that opens up and releases the water pressure off of the coffee and deposits it into the drip tray when the brewing process is complete. When we backflush we utilize this pressure release to blow cleaner up into the brewing components.
The cleaner will remove the old coffee oils and deposits that can cause your coffee to taste bitter and rancid. It will also prevent coffee from building up on the shower screen that eventually plugs it up. If you ever see small high-pressure streams of water coming from the shower screen you know it is plugged and is restricting the water flow.
Go ahead and remove the screen and hold it up to the light. You will be amazed at how any water gets through it at all. The bottles of cleaner come with instructions but I will go over one method briefly in the following paragraph.
How To Backflush
- Remove your filter basket from the portafilter and put in a backflush disc. This disc can either be a filter basket with no holes in it (also called a blind basket) or a rubber disc that fits over the holes of a single shot filter basket.
- Spoon approximately 0.5 teaspoons of backflush cleaner into the basket.
- Put the portafilter back into the brew group and turn on the pump.
- In about 20 seconds the pump will get very quiet. This is a result of the pressure now being built up. When the pressure has built up (quiet), turn off the pump.
- You will then hear a “whoosh” sound as the cleaner gets blown up into the brew group, through the three-way valve and empties into the drip tray. Repeat this process until the foam coming out into the drip tray is clean.
- Remove the handle and rinse the cleaner out of the handle. Put the handle back into the machine again and do a couple more backflushes without cleaner…using just water.
- Lastly, remove the handle and turn the pump on and off a few times to rinse the remaining cleaner out of the brew group.
Commercial & Semi-Commercial
Any semi-commercial or commercial machines such as the ECM, Rocket Espresso or Pasquini should be backflushed on a regular basis. When the machine is being used in a commercial application the machine should be backflushed at the end of every day. For home users who are real particular, backflushing could be done every day though once or twice a week would be adequate.
If you have one or both of the following symptoms your three-way valve may need cleaning.
- You notice reduced brewing pressure due to mineral buildup in the three-way valve and are sure it’s not a result of a clogged shower screen (check this first).
- You have a constant dripping through the three-way valve when you are brewing your espresso or while the machine is sitting idle (while hot).