I just ran the WASH cycle (without detergent).
A couple of notes and observations for the record:
- Took about 15 minutes to run.
- It would "brew" about 150ml of water every few minutes until the tank is emptied
- Once emptied it would not perform a rinse cycle with an additional tank like DESCALE does.
Given the lack of a rinse cycle I suspect that whatever detergent it wants, it probably has to be poured using the pre-ground opening on the top unless you like detergent-flavored coffee.
I STRONGLY ADVICE AGAINST ADDING DETERGENTS TO THE TANK when using this function, at least until we find out how to correctly using this function.
I found this fixya link
Long story short, the wash programs does a high tech cleaning of the machine. You should use coffee machine cleaners like Cafiza, Puro Caff or Joe Glo. The detergent should be poured using the pre-ground hole at the top.
I bought a bottle of Cafiza and poured about a spoonful through the pre-ground chute and ran the WASH cycle, photo below shows what was coming out (I had already emptied the glass jar once, what initially came out was plainly gross I should have taken pictures). It's surprising considering that I had disassembled and cleaned the entire brew unit 2 days ago in order to replace an aging o-ring.
Once it was done, I took out the brew unit, rinsed it with water just in case and brewed and discarded one coffee. After that I brewed a new coffee and it definitely tastes better now, less acidic and more "round" around the edges. I'm using a custom blend of 78% Brasil Santos + 22% Colombia beans made by my friend.