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DeanOK
Senior Member
DeanOK
Joined: 24 Sep 2012
Posts: 693
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Sun Jun 22, 2014, 9:07am
Subject: Newer V2Bs: Do they have the cavitation issue?
 

Just wondering?? One of my big disappointments in this product was that there was no serious effort from QM or the distributor to solve this issue.  I wonder if it was solved in later versions and how they fixed it. I have to deal with this issue almost every day and I don't think I should have to be dealing with it.
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,452
Location: UK
Expertise: I love coffee

Posted Sun Jun 22, 2014, 1:45pm
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

DeanOK Said:

Just wondering?? One of my big disappointments in this product was that there was no serious effort from QM or the distributor to solve this issue.  I wonder if it was solved in later versions and how they fixed it. I have to deal with this issue almost every day and I don't think I should have to be dealing with it.

Posted June 22, 2014 link

UK ones definitely don't dean, I think the slightly higher pump speeds of the US variants have just found the tipping point. I advised QM to increase the feed-pipe sizes to the low pressure side of the pump which should resolve the issue.

Something you could try is to take the mains plumbing tube and place it into a bottle of water on the counter....use it from the bottle for a few days and see if the problem goes away. if it does then it indicates the path from that fitting is of sufficient size to prevent any cavitation, this might mean simply increasing the feed tube size from the tank to the first fitting it comes to!

Dave
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DeanOK
Senior Member
DeanOK
Joined: 24 Sep 2012
Posts: 693
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Sun Jun 22, 2014, 2:02pm
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

DavecUK Said:

UK ones definitely don't dean, I think the slightly higher pump speeds of the US variants have just found the tipping point. I advised QM to increase the feed-pipe sizes to the low pressure side of the pump which should resolve the issue.

Something you could try is to take the mains plumbing tube and place it into a bottle of water on the counter....use it from the bottle for a few days and see if the problem goes away. if it does then it indicates the path from that fitting is of sufficient size to prevent any cavitation, this might mean simply increasing the feed tube size from the tank to the first fitting it comes to!

Dave

Posted June 22, 2014 link

Thank you.... I will tell you why I am not sure I agree with you, but I don't want to appear to be challenging you because I really do not know the answer.

The reason I am not sure a larger tube will fix the issue (for me) is because air forms at the highest point in my pickup tube when the unit sits for several hours. It is also important for you to know that I leave my unit on 24/7 and the heat may be adding to my issue. At any rate, the air that is formed and rises to the top of the tank pickup tube is the air that I think is sucked into the pump and causes the issue. It may not even be fair to say it is cavitation specifically because technically it is a pump with air in it if my theory is correct.  Also, I have checked and there is no leakage of any of the tubing. I have attached a photo to this post of the air that forms in the pickup tube. The air in the tube is actually much more than the air that is photo when it sits for several hours.

I do understand how a larger tube could help solve cavitation, but I am not sure it will help much if air is actually drawn into the pump.

With all that said, I probably could solve my particular issue entirely by plumbing it in. While it is easy for me to get water to my unit, I don't want to make modification in my kitchen cabinetry because my long term plans are not to leave the machine where it is now.

What I do now is turn the main valve on without the PF in place until pump pressure comes up. If the machine has been used in the last hour or so, the pump pressure will come up immediately. If it has been sitting for 6 to 8 hours or longer, there is quite a delay in the pump pressure coming up while the pump struggles to prime itself. Also, if I were to go by every hour or two and run a small amount of water through the brew head, the pump would prime immediately every time and it would never have the cavitation issue.

DeanOK: V2V_bubbles_small.jpg
(Click for larger image)
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,452
Location: UK
Expertise: I love coffee

Posted Sun Jun 22, 2014, 4:11pm
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

DeanOK Said:

Thank you.... I will tell you why I am not sure I agree with you, but I don't want to appear to be challenging you because I really do not know the answer.

The reason I am not sure a larger tube will fix the issue (for me) is because air forms at the highest point in my pickup tube when the unit sits for several hours. It is also important for you to know that I leave my unit on 24/7 and the heat may be adding to my issue. At any rate, the air that is formed and rises to the top of the tank pickup tube is the air that I think is sucked into the pump and causes the issue. It may not even be fair to say it is cavitation specifically because technically it is a pump with air in it if my theory is correct.  Also, I have checked and there is no leakage of any of the tubing. I have attached a photo to this post of the air that forms in the pickup tube. The air in the tube is actually much more than the air that is photo when it sits for several hours.

I do understand how a larger tube could help solve cavitation, but I am not sure it will help much if air is actually drawn into the pump.

Posted June 22, 2014 link

The air must be coming from the anti backflow valve...remove, clean, check, refit.
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DeanOK
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DeanOK
Joined: 24 Sep 2012
Posts: 693
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Sun Jun 22, 2014, 4:28pm
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

DavecUK Said:

The air must be coming from the anti backflow valve...remove, clean, check, refit.

Posted June 22, 2014 link

Where is it? I don't recall a backflow valve or check valve ever being mentioned on this model.
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sharky
Senior Member
sharky
Joined: 9 Jan 2013
Posts: 186
Location: Calgary, AB
Expertise: I love coffee

Espresso: QM Vetrano 2B
Grinder: Compak K3 Touch
Posted Sun Jun 22, 2014, 9:06pm
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

Dean, I have the same (cavitation) issue every once in a while.  I have mine on a timer so it is all warmed up when I wake up.  I only have the brew group switch on & if I lift up on the lever and it growls, I push it back down immediately & re-lift it again.  The growl is gone and I dispense some water through the group, flip on the boiler switch and 10 minutes later I am ready to make my latte.  Why does it do the cavitation thing . . . I don't know.  It doesn't do it every time and others have said it is not harmful so I am not going to worry about it!  I love my Vetrano 2B and it makes amazing espresso!  The growl sound isn't a big deal for me so I live with it . . .
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,452
Location: UK
Expertise: I love coffee

Posted Mon Jun 23, 2014, 3:09am
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

Mine is here

DavecUK: abvalve.JPG
(Click for larger image)
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CarloM
Senior Member


Joined: 1 Apr 2013
Posts: 332
Location: Los Angeles
Expertise: I live coffee

Espresso: Vetrano V2B
Grinder: Mazzer Mini-E Type A, SJ...
Drip: Toddy
Posted Mon Jun 23, 2014, 8:42am
Subject: Re: Newer V2Bs: Do they have the cavitation issue?
 

It's funny how random this is. Mine didn't do it for the first month plus of ownership, then did it about 30-40% of the time for many months. About a week ago I thought "wow I haven't heard the cavitation in quite a while" meaning maybe up to a month or more. Then it happened. :( Off an on again in the last week, about 1/3 of the time.

On a side note, I've always had some spritzers and channeling out of my bottomless portafilter, using an 18g VST ridgeless basket, even after doing the WDT. Much less than with my old Rancilio Silvia, but still enough so that I don't leave the cup sitting on the reservoir screen when I draw a shot because I don't want the spritzing to go outside of the cup, I hold it up right under the portafilter.

Well I read somewhere (maybe a post here?) that sometimes the shape of the tamper may make a difference, and that ideally it should be the same shape as the bottom of your shower screen. I have a convex tamper and looking at the bottom of the VST, it's pretty close to flat. So yesterday while at Intelligentsia I bought a Reg Barber tamper with a flat base.

This morning I used it for the first time, did the WDT, and for my first double shot, zero channeling/spritzing. No other changes, the beans were the same as yesterday, and the grind and dosing were unchanged. For the first time in memory, the sides of the cup were unbroken white, not dotted with coffee spray. Of course this is just the first time, the key will be repeatability, but if it holds, then I'll be darned...the tamper base shape does make a difference!
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Tonyv138
Senior Member


Joined: 16 Jun 2013
Posts: 74
Location: tx
Expertise: I love coffee

Espresso: V2B
Grinder: Mazzer SJ
Posted Fri Jun 27, 2014, 6:01pm
Subject: Feedback on Dave'suggestion - Re: Newer V2Bs: Do they have the cavitation issue?
 

DavecUK Said:

UK ones definitely don't dean, I think the slightly higher pump speeds of the US variants have just found the tipping point. I advised QM to increase the feed-pipe sizes to the low pressure side of the pump which should resolve the issue.

Something you could try is to take the mains plumbing tube and place it into a bottle of water on the counter....use it from the bottle for a few days and see if the problem goes away. if it does then it indicates the path from that fitting is of sufficient size to prevent any cavitation, this might mean simply increasing the feed tube size from the tank to the first fitting it comes to!

Dave

Posted June 22, 2014 link

I did the experiment - connected the external water feed to the machine and feed water from the bottle. Still cavitates.

I admit, I have not opened the machine to look, but hope someone knows off the top of their head - what is the fluid o'tech model pump is used in V2B?

Thanks
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