Water flow through the group screens

Did your new VII work fine initially but have an in warranty (year one) problem later. Post here for advice. Later report on your fix. Posted photos documenting repairs are encouraged.
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coffeeowl
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Water flow through the group screens

Post by coffeeowl » Sat Jul 19, 2008 8:49 pm

Hi!
I noticed that water flow through the group screens differs each time I pull water with portafilter removed. I started paying attention to it when I noticed some not-so-even extractions. First I thought I needed a good chemical backflush, but that didn't help. At times the flow is even, but usually there are some tourbulences, or the flow changes. Sometimes it looks and sounds like some air coming out together with the water. Any thoughts?
Thanks!
Pawel

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Re: Water flow through the group screens

Post by Niko » Sun Jul 20, 2008 8:44 pm

The only thing that comes to mind is one of those notorious brass shavings found in the valves.
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Re: Water flow through the group screens

Post by coffeeowl » Mon Jul 21, 2008 12:42 pm

If so, what to do?
Anyway..., would something stuck in the water pathway affect the water flow through screens? I thought it's the machine's need for caffiza showing up.
Would you be willing to make a video of water flow with no portafilter in the group? (please :) )
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Re: Water flow through the group screens

Post by JohnB » Mon Jul 21, 2008 2:56 pm

Have you dropped the screens & checked to see if you've got a layer of old grounds up there?
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coffeeowl
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Re: Water flow through the group screens

Post by coffeeowl » Tue Jul 22, 2008 11:45 am

Yes I did. In fact I do it regularly, however I'm too lazy to do it every evening (or shall I say everynight - I have a go before bed quite often). The problem started when I first turned off the machine for a week, when I was away from home. My mistake was that I didn't do caffiza before turning it off (I run it on all the time). La Spaziale is to blame as I simply believed the manual - they say no chemistry so I didn't have caffiza at home at all (and it is stupid advice, scary that manufacturer does give it).

I do paolo brush, portafilter water dance and backflush after every coffee session (even if it is just one cup).

I soaked the screens and diffuser in caffiza for 30 minutes, I did caffiza backflush, then water, then caffiza again, then plenty of water. I also did backflush it with screens off (just the diffuser). Now it looks quite good, but it seems to me that the real reason was how tight/loose the screens and diffuser were assembled to the group and what is left on the group when the machine is idle - I used to leave portafilter with blank filter but then changed to leave the naked with a basket - that makes the group going dry.

I think I should post a video myself - probably during weekend I'll make it.
Pawel

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Re: Water flow through the group screens

Post by coffeeowl » Sun Aug 10, 2008 5:36 pm

Quite surprising solution to my problem... While the group was operating I lifted the water inlet tube up and noticed that the pump sound changed to smoother. Then I put the inlet on a thick showel - now the pump goes much much smoother and the water flow is even!
I would never think of that myself.
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Re: Water flow through the group screens

Post by chas » Sun Aug 10, 2008 8:26 pm

Do you have any theories as to why that would make a differnce????
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Re: Water flow through the group screens

Post by coffeeowl » Mon Aug 11, 2008 6:00 pm

I have no idea. It looks completely crazy.
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Re: Water flow through the group screens

Post by Weska » Tue Aug 12, 2008 3:26 pm

Maybe variation in or absence of water pressure left an air bubble in the line. Maybe aeration in the water gathered to form a significant vapor lock or bubble during that idle week.

The bubble stayed and made the pumped water surge at times with air, but it remained mostly in place lodged somewhere in the line. Moving the line around allowed the bubble to be dislodged and completely pumped through.

Apart from that, I'm out of ideas, coffeeowl.
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Re: Water flow through the group screens

Post by coffeeowl » Tue Aug 12, 2008 6:49 pm

I don't know really.
Definitely it has something to do with the vibrations of the inlet line. If it vibrates smoothly, then the flow is even. I checked the valve - it is open. Everything looks the same as it was. If there was a bubble it should get pumped through, anyway I can't imagine how it would get there.
Pawel

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