The Backflush Controversy

Glenn drops in with another word about keeping it cleanGlenn takes a long, hard look at the coffee oils building up within his Gaggia Classic and considers that great question of divide between manufacturers and consumers of domestic espresso machines ... am I allowed to backflush?

For the uninitiated, backflushing is a regular maintenance task for commercial espresso equipment and, I would recommend, also to be performed with domestic machines sporting a so-called "3-way" solenoid valve. After pulling a shot, the solenoid vents excess water and pressure through a waste tube to the drip tray. This means that coffee oils travel back through the screen, the valve, and the waste path, and can build up over time. Backflushing with an appropriate coffee detergent will help to keep everything clean and ship-shape. Be sure to flush copiously with clean water after backflushing, to avoid drinking detergent -- discarding an initial sink shot is often recommended with this in mind. Also, take care not to confuse coffee detergents with descaling agents, as the detergents should stay on the outside of the machine, away from the boiler.

Every morning, I flush about 250ml of boiler water on my Gaggia Classic and I stare into a white ceramic cup filled with brackish coffee coloured water complete with a dollop of coffee grounds.

Peering into the cup, there is no doubt that the brew water is being contaminated by something. Yesterday’s coffee? Or heaven forbid, last week’s coffee?!!!

Is backflushing my machine going to help me make a better shot this morning? “Of course it will,” a little voice says. It has always been recommended by the pros. You must backflush.

Another voice says: “Don't be silly. Your machine is not designed for backflushing. You do not have a commercial machine. You pull just a double or two a day. Just because it can be done does not mean it should be done. You’ll break something.”

Most experienced espresso enthusiasts heartily recommend backflushing because it has been traditionally thought that espresso can be contaminated by residual, rank and rancid coffee oils caught along the brew path.

So, should solenoid-equipped Silvias, Gaggias and other similar non-E61 machines be backflushed? Yes, no, maybe, perhaps? How often?

The manufacturers say no and most espresso equipment retailers also say no ...yet there is a hard core of espresso aficionados that swear by the accepted doctrine of backflushing.

Maybe the backflush camp has a point. You go through all of the trouble to grind your shot exactly and tamp perfectly, only to dump dirty water all over your carefully prepared puck!

However, before we start taking out the chemicals and the blind filter basket, perhaps we should first look at other aspects that directly affect the overall cleanliness of your machine.

When was the last time that you cleaned the shower screen? Remove it and take a look. Yup, lots of fine silt of something or other. Hmm ... the group head is not looking all that sanitary either. If you are a milk drinker, steam mode has nicely baked all kinds of muck on the group head. Might as well remove it, too, and clean thoroughly.

Reassemble everything, flush with plenty of water and then backflush with a chemical cleaner. Backflush and rinse with fresh water aplenty.

The controversy whether you should backflush or not seems to be centered on the possibility of equipment damage cause by the very high backpressure.

Here is a good compromise. You do not need to slam your machine with 15 bar of pressure to actuate the solenoid valve. And rapidly flicking off and on the power to your machine will do nothing to extend the lifetime of its electrical components.

You don’t need a sledgehammer to drive a nail so I think the rubber plug method to backflush would be far more forgiving than using a blind filter basket. Messier perhaps, but properly done, it shouldn’t put much more strain on your machine than pulling a shot.

So here it is, the definitive word: backflush if you wish, during your annual, semi-annual, quarterly, monthly, weekly or daily cleaning. Use chemicals or water (your choice). Keep your machine clean. Backflushing by itself is not enough. Use the rubber plug method if you want to be certain about not damaging anything. Concentrate on your tamping technique. Buy or roast good beans. A god-shot will certainly follow at some point.

That’s it, the final word. I am quite sure of it.

Related articles: Group Disassembly Recap , Gaggia Step by step v1.0

Glenns is a Contributing Editor for…controversy is his middle name.

Editor's Comment: Backflushing should place no more stress on a solenoid-equipped domestic machine than a stalled shot or even a tight ristretto. No worries, but use common sense and remember that ulka pumps are not meant for long duty cycles. --Dave