This is something I've been curious about for awhile now: If I pull the lever up to brew mode with NO portafilter installed, what should the water dispersion look like coming out of the dispersion screen? I've seen some videos where the dispersion is almost like an even rain shower across the whole screen. My machine has never performed this way; the normal water flow pattern for me is two distinct streams occurring about 5mm or so away from the dispersion screw. I get some random drips near the outer diameter of the screen but nothing consistent.

I bought my machine used and 8 months later I'm still learning how to pull a good shot with a naked portafilter. I often get a nice central pour with no obvious channeling but the tiger striping is really wobbly and inconsistent. Sometimes, however, I get two distinct streams of espresso for about 10 seconds and I'm curious whether I have some kind of water dispersion issue.

Thanks for the help!

Joe.

The E61 group has a sloped water passage going into the shower screen, and will only rarely flow out evenly. But it does not matter in this case, since there is a gradual preinfusion, along with space over the top of the shower screen where the water can pool. This means the water always hits the puck gently. Groups without preinfusion or space above the shower screen should be designed to flow evenly, and usually require head space between the puck and shower screen as well.

Thanks Jim! Unfortunately I think my grinding/dosing/tamping technique is the issue.

You may be right about the cleaning. I don't think removing and cleaning that dispersion screw was part of normal maintenance; I never even did it when changing gaskets on my Tea. Descaling kept it clear, but it may have had enough gunk to alter the flow pattern.

There are also several different kinds of E61 shower screens out there. I remember some were easier to to maintain than others, but I cannot recall if they also affected the way the water flowed.

But my main point is that with the long preinfusion, and all the space, uneven flow is not a shot killer.

See Off centered water dispersion

Yup, seems like a definite asked and answered topic