Backflushing Refresher Course!

I got an email from a barista last night who was having trouble some issues with backflushing:

I have a 5 group head La Marzocco and I daily backflush with water and detergent. I now know there is a huge debate on backflushing with/without the screen. That ISN’T my question. How long do you backflush with the detergent? with the water? The manual just says run with blind filter and detergent. No specifics. How long until it effects the solenoid valve? Should I turn it off and on 10-15 for 3 seconds each, or 8 times at 15 second each?? This is driving me crazy!! Do you have an article related to this topic or know where I might be able to find more information directly about this?

I dug up some great articles we’ve published over the years on espresso machine cleaning and general preventative maintenance. Since she cited her La Marzocco, I also cc-ed my friend Ryan Willbur who works at La Marzocco USA, to see if he had any specific comments. This is what he told her:

Here’s what I have experienced-  
  • Espresso machine cleaner does the most work when the group head is turned off. When the group is running, water and cleaner are circulating through the machine. When the group head is turned off, the cleaner is able to eat up all the oils and grime that build up in the machine.  
  • Make sure to dissolve the cleaner before you start to backflush. If you do not do this, you are simply sending clumps of soap into the group. The cleaning agents are not fully active until they are dissolved in water. So, add a little bit of cleaner to the backflush disk, add some hot water, and let the elements sit for 15 seconds or so until they create a liquid cleaning solution.
  • Cleaning the machines at La Marzocco, I tend to run each group head for 10 seconds, before turning it off for another 10. I repeat this about 5 times. Then, I take off the porafilter and rinse out the group for 10 seconds or so. Finally, I repeat the 10 seconds on, 10 seconds off with clean water, making sure to get the rest of the cleaning solution rinsed from the group.  

This whole exchange made me think, hey! Let’s post a guide to back flushing! Pro baristas and novices alike can always benefit from a little review. This is what Matt Milletto, the Director of the American Barista & Coffee School, advises:


1) Remove the portafilter basket and replace with a blank portafilter basket, i.e. basket without a screen, also called a blind basket

2) Put approximately half a teaspoon of espresso machine cleaner into the blank portafilter basket. Follow cleaner manufacturer’s suggested volumes.

3) Insert the portafilter into the grouphead of your espresso machine securely, and engage the machine as if you wre extracting espresso. After roughly 20 seconds this will cause water to back up and build pressure. Now release the pressure by disengaging the pump and the water will flush through the grouphead via a three-way valve, ending in the drip tray in the machine.

4) Backflush with the detergent a few times, using 15 “20 second intervals. Remove the basket and you will see the detergent and coffee oils present. Make sure that the grouphead has been flushed thoroughly.

5) Remove and rinse the portafilter and basket using water from the grouphead. Make sure to run water through the grouphead.

6) Once clean of detergent, backflush the grouphead a few times to remove any residual detergent. Do not add more detergent.

7) Use a grouphead cleaning brush to remove any residual coffee grounds and oils from the group and gasket. Also scrub the dispersion screen. After brushing, use a wet terry towel to clean off the gasket and around the sides of the dispersion screen and grouphead.

8) If necessary, remove the dispersion screen and soak in detergent and hot water to remove caked-on coffee residue and grinds.

9) Once again, remove the portafilter and rinse the grouphead clean. Replace the blank portafilter basket with a normal filter basket.

10) To season the grouphead, and to ensure that there is no detergent residue, pull two or three shots through each grouphead that has been cleaned.

(Optional: Take a damp terry towel and wrap it around your hand while holding the portafilter to insure that you won’t burn yourself. Now engage the pump on the machine so that hot water is flowing through the grouphead. Slowly insert the portafilter into the grouphead without creating a seal. Do this a few times, letting the water flow around the portafilter. This will help remove hard to reach coffee grounds that a brush can’t get to.)

This was fun! Do you have any questions you’d like our expert peeps in the industry to answer? Just send them my way!

Happy cleaning!


About Sarah 933 Articles
Sarah Allen (she/her) is co-founder and editor of Barista Magazine, the international trade magazine for coffee professionals. A passionate advocate for baristas, quality, and the coffee community, Sarah has traveled widely to research stories, interact with readers, and present on a variety of topics affecting specialty coffee. She also loves animals, swimming, ice cream, and living in Portland, Oregon.