I have a Rancilio Silvia espresso machine. When brewing, there is a slow drip through the middle of the portafilter in addition to the two streams of espresso flowing through the proper side channels. Is this a sign of overfilling, too fine a grind, or of portafilter being broken? Thanks for any info!

Please post a photo so we can see what you're describing.

evdvelde wrote:I have a Rancilio Silvia espresso machine. When brewing, there is a slow drip through the middle of the portafilter in addition to the two streams of espresso flowing through the proper side channels. Is this a sign of overfilling, too fine a grind, or of portafilter being broken? Thanks for any info!

Sounds like you're coffee puck has poor consistency. Too dense in the center forces the fluid to travel around the restriction, such as your case to the sides, which explains the side channeling. There is no such thing as "proper" side channels, unless I am somehow misinterpreting what you mean by that.

Have you tried redistributing after grinding? It's just a matter of stirring the grounds for even fines distribution across the puck.

'Proper side channels' = two-spouted portafilter?

Without fully understanding what's happening, I would first ask, have you checked/changed the gasket behind the showerscreen?

Thanks for the input. Just after I posted my question, we changed to a new coffee and adjusted the grind. The problem has disappeared. So, it is clearly related to the grind and/or tamping. We had it on a fine grind.
BTW, I did mean the two spouts of the portafilter when I mentioned "side channels".

Good that the problem is sort of 'solved'.
If I were you I would still check the gasket, because the portafilter should not leak.
Instead grinding too fine should choke your machine - not cause a leak.
If there's a leak you're losing pressure. You don't want that.