This article applies to the Gaggia,Silvia and similar solenoid equipped machines.

First of all, DO NOT BACKFLUSH an espresso machine that is not equipped with a solenoid. BAD things can happen. Yes, there are some manufacturers of solenoid equipped machines who do not recommend backflushing for their consumer machines, but the general agreement among the pros is that there are definite benefits in doing so.

What's a solenoid valve?

An espresso machine with a solenoid valve allows you to remove the portafilter right after you pull the shot. As soon as you turn off the brew switch, this valve instantly opens, releasing the high pressure from the filter basket and diverting it to the drip tray. So, if you wanted to pull another shot, you could immediately remove the portafilter and reload. For machines without this type of valve, you have to wait for the pressure to subside by itself or suffer the indignity of a portafilter “sneeze” – an explosion of very hot water and coffee grounds. Messy and not very safe either.

Why backflush at all?

It is quite likely that a solenoid valve can survive for years being coated continually in coffee oils, coffee grounds and gunk. Until one day, it will either get plugged or not work at all. Secondly, all this dirt and corruption may be affecting the taste of your shot.

Backflushing preparation:

Backflushing should be part of your weekly maintenance schedule.

• clean and refill the water reservoir

• remove and clean the showerscreen

• cleaning the group head (accessible after removing the showerscreen)

• flushing the group with water

Ok, the reservoir is clean, the screen is clean and the group is clean. The water coming out of the group should be absolutely clear and there should not be any visible coffee grounds in the flush water.

Backflushing methods:

You can use either a special backflush filterbasket (a filterbasket with no holes) or a rubber backflush disk that you insert in your double filterbasket to stop the flow ofwater.

In this article, we will use the rubber backflush disk as it is more “forgiving”. Plus, if you want to clean your group between multiple shots, you can just plop it in your filterbasket and do the “portafilter jiggle” without doing the hot potato routine with a very hot basket.

The instructions

1. Get a cleaning agent. There are special backflushing compounds that will do the job. If you are in an experimental mood, both Colin and I use dishwasher detergent to backflush. Notice I said dishwasher detergent – not dishwashing detergent. Just a pinch at a time will do .

2. Remove the drip tray cover so you can see what's going on. Use precautions and guard yourself against splashes.

3. Heat your machine so at least it's warm.

4. Insert the rubber plug in your double basket.

5. Put the cleaning solution, slurry, paste (depending on the product you are using) in the basket.

6. Insert the portafilter into the group.

7. Turn on the brew switch for about 3 seconds or so.

8. Turn off the brew switch

9. Observe the satisfying “kerr-sploosh”

10. Repeat three times and backflush with clear water a few times more.

Because the rubber disk is not completely watertight, you will have time to gradually ramp up the pressure. You will hear the pump start to work at little harder. Don't push it too far. It will be most definitely less than 5 seconds. You will soon be able to judge the optimum time to turn off the switch. Do not get carried away. Do not be tempted to backflush several dozen times in quick succession.

Finishing up:

Some of these cleaning powders are difficult to dissolve. Remove the showerscreen again. Clean again. Flush lots of clear water through the group. Use clean cloths. Do the portafilter jiggle to thoroughly clean the group gasket area. Re-assemble. Prepare a espresso shot. Discard.

You will be rewarded with a much cleaner machine and better tasting espresso!