Okay, because I got my yummie taste back by lowering the temperature, I did not bother to do another descaling yet, I have to admit

. The leakage is a little less after these two weeks, but there is a thing I can't explain: the machine is leaking heavier when I am brewing than when I do a backflush. Does anyone have an idea about this? When I backflush it is only a few drops, but when I am brewing it really drips...
The former owner lives on the other side of the country (which, by your standards is still quite nearby (300 km.)

), so I do not know what kind of water he used. I imagine that his maintenance was not all that thorough.
The first descaling took me two hours. I think I will do another, extra long, descaling one of these days. Unfortunately I don't know how to overfill the boiler. The descaler I use is meant to be used quite cool, so not in a heated boiler. Supposedly it will start to foam or something.
Well, thanks again for helping, and I'll report back when I did my second descaling...