kolu wrote:always backflush with the shower screen on.

except for when you completely dissolve the detergent first.

undissolved detergent tends to accumulate (not only) in the three-way valve during backflushing without the screen...

First I hear of this. Any source for this?

I ask since the choice of 3 chemical - being highly dissolvable (think airborne like dissolve) was a key parameter.

kolu wrote:always backflush with the shower screen on.

except for when you completely dissolve the detergent first.

undissolved detergent tends to accumulate (not only) in the three-way valve during backflushing without the screen...

So undissolved detergent might go into the 3-way valve and... what? Magically become insoluble? If it can't be dissolved inside that valve by ample volumes of 200°F water passing through the valve under 130 psi or higher pressure, how does one dissolve it?

Sorry, but I've heard this before from people, and it seems like magical thinking to me.

But to the empirical point, I have done exactly what you say not to do, several days a week, for at least 5 years. I opened up my 3-way solenoid on my GS/3 a few times a year when I had it. I have never seen the slightest sign of detergent accumulation. It does not happen.

I've already seen LM Strada with almost clogged 3-way valve by Cafiza. Go figure yourself.
Also it mostly happens when people don't rinse the machine enough at the end of the shift - there are traces of chemicals in the water already in the pipes which will dry up overnight and begin to slowly accumulate (it was probably combination of both) behind sharp edges.

Sounds like you're describing a situation where people are using way too much detergent and not rinsing properly. Sure, soluble chemicals dissolve at varying rates. If you stuffed a huge amount of Cafiza up the feed tube, you could probably clog the machine before water could dissolve it all, and being clogged, water wouldn't be able to contact it sufficiently to do so. But that is IMO an exceptional combination of stupid mistakes, and backflushing without a screen, while it prevents the consequences of the two stupid things, isn't itself a mistake.

I have seen baristas do some monumentally dumb things to espresso machines. That should not be the basis of giving advice to others, especially in an unqualified way as you initially did. Better to say-rinse your machine thoroughly after a backflush, and use the correct amount of detergent, which is not much at all.

What awful coffee that clogged machine would pull. Cafiza is horribly bitter.

How does the Cafiza clog survive the 9bars or so of pressure? Are you sure it isn't scale or some other mineral deposits?

Perhaps the Cafiza deposits were only in the exhaust of the 3way, so it would not affect flavor, nor be affected by the pressure.

brianl wrote:backflushing doesn't remove the need to remove the screen weekly to clean. However, for the everyday backflush i'd leave it on.

Agree need to remove the screen to completely clean/wipe above the screen but not the screen itself.

Pictures of screen after 1 week use (around 45-50 double shots) water back flushing after every session even if only one shot pulled. (screw not loosened during back flush)
Note: post session water back flushing I don't run a full 10 back flushes like I do with detergent. Usually about 4 manual cycle engaging pump wiggling PF with blank until water flows out and around then lock for a couple seconds disengage pump and repeat.



After my weekly detergent back flush with screen in screw slightly loosened during back flush. IMO zero need to soak screen.
Note: running Slayers built in 10 back flush cycle.



The only time I find it necessary (home or business machines) to soak a dispersion screen is if it has been neglected and is caked with hardened crap from long abuse.

Working for a whole sell roasting company. Our training department trains cafes to backflush with screen in.