# Groaning from Duetto II



## christos_geo (Feb 9, 2016)

So I'd like to pick your brains about this one. I'm slightly concerned about some strange noises coming from my Duetto II. Let me explain..

Following daily 2hr warm up, the initial water pumped through makes this loud groaning noise with flickering of brew pump pressure (video link attached at bottom). After a couple times of 'purging' what I think is air in the inlet tube, flow, pressure and sound returns back to normal. Inlet tube after warm up and before initial activation of brew lever appears to contain a large air pocket. Could this be the problem ? And could this be caused by a leaky anti backflow valve or expansion valve issue?

This has always been happening as far as I'm concerned and although I've not noticed any detrimental effects I would like to know if there is a fix for it. I read a couple of detailed posts by @DavecUK regarding a similar topic and wanted to understand if what I'm facing relates to the same problem.

Machine is in absolute pristine condition and volvic or waitrose bottle water fed only. Also inlet tube is cut as v at bottom so that shouldn't be causing blockage.

As I said it doesn't cause an actual problem, just rather it sounded smooth at all points. Not checked under the hood for any of the aforementioned issues yet.

Cheers guys!


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## DavecUK (Aug 6, 2013)

Air in the line, presumably because of anti backflow valve leaking back...need to clean or replace.


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## christos_geo (Feb 9, 2016)

Thank you!


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## whip (Jul 9, 2016)

Mine made this kind of of noise when when the mains pressure was too low. I appreciate yours isn't plumbed in but could be a blockage or kink in a pipe restricting the flow?


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## DavecUK (Aug 6, 2013)

whip said:


> Mine made this kind of of noise when when the mains pressure was too low. I appreciate yours isn't plumbed in but could be a blockage or kink in a pipe restricting the flow?


This post was months ago, would have been nice to get a confirmation of whether the problem was solved or not, but so often people never post back to the thread. In this way others don't benefit from what might have been a solution, so it's a little bit lazy and selfish. It's also a pity, because I never learn more about what it actually was and it's like throwing knowledge into the darkness without feedback. After a while you don't know if it was right or not, then eventually you stop caring and stop responding to so many help requests.


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## christos_geo (Feb 9, 2016)

I truly apologise @DavecUK, you are absolutely right and I am terribly sorry for perhaps coming across as selfish, not intentional whatsoever.

Truth is that a standard descale did nothing for the groaning so I went ahead and opened up the machine. Removed the case and the controller as per your instructions and then faced a road block. I couldn't for the life of me remove the water base plate, or I think that's what it's called, and hence could not get to the anti backflow valve. I reopened the following day thinking I must have missed an obvious screw but again couldn't work out how to get past that and couldn't find anything online explaining it and may have been a bit embarrassed to ask... I gave up and decided to molykote my rotary pump instead to make me feel better....







noise is still very much there and annoying me beyond belief. I now bleed the first water through the water pipe until pump is engaged which makes the groaning slightly more bearable. Interestingly though, if I only have the brew boiler turned on, no matter how many hours pass before pulling water through, I never get any of the groaning.

I really want to get to the bottom of this and will most definitely report back soon as I've got my mitts on that bloody valve!


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## PaulL (May 5, 2014)

I'm not the most technical and so can't recall if I have touched the anti back flow on my Duetto but on my previous Alex MKII Dave 'encouraged' me to write an article on it which you may have already found http://coffeetime.wikidot.com/izzo-alex-anti-backflow-also-called-non-return-valve

I tell you, it wasn't easy for me and it won't tell you how to unscrew everything but you may find it useful if you haven't read it.


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## Nikko (Aug 20, 2014)

You say that a) the pump noise gets better when you remove some water from the steam boiler and that b) the noise disappears completely if the steam boiler is switched off.

Not sure why a) should have anything to do with it at all, and as for b) the only other connection from the steam boiler back to the pump is via the fill solenoid. May be that is the culprit? Another possibility is a split in the HX. Is the steam boiler working OK?

As regards the NRV, a better design would probably have been to connect the brew HX into the steam boiler from the top so obviating the need for both the NRV and the expansion valve.


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## Glenn (Jun 14, 2008)

Duetto II is a Dual Boiler - not an HX machine


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## Nikko (Aug 20, 2014)

Glenn said:


> Duetto II is a Dual Boiler - not an HX machine


Very true... but it does have an HX through the steam boiler to preheat brew water


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## christos_geo (Feb 9, 2016)

PaulL said:


> I'm not the most technical and so can't recall if I have touched the anti back flow on my Duetto but on my previous Alex MKII Dave 'encouraged' me to write an article on it which you may have already found http://coffeetime.wikidot.com/izzo-alex-anti-backflow-also-called-non-return-valve
> 
> I tell you, it wasn't easy for me and it won't tell you how to unscrew everything but you may find it useful if you haven't read it.


Thank you @PaulL, I did in fact find your article and was delighted about the amount of detail you went into concerning the exact problem I am facing! Had it open and used it as a manual while unscrewed all the bits and pieces. Got stuck at the water plate removal stage prior to the water sensor disengagement as I couldn't find an obvious screw holding the plate in place. Do you by any chance remember how you went about removing it?

Thank you!


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## christos_geo (Feb 9, 2016)

Nikko said:


> You say that a) the pump noise gets better when you remove some water from the steam boiler and that b) the noise disappears completely if the steam boiler is switched off.
> 
> Not sure why a) should have anything to do with it at all, and as for b) the only other connection from the steam boiler back to the pump is via the fill solenoid. May be that is the culprit? Another possibility is a split in the HX. Is the steam boiler working OK?
> 
> As regards the NRV, a better design would probably have been to connect the brew HX into the steam boiler from the top so obviating the need for both the NRV and the expansion valve.


Thanks @Nikko, the only reason the pump noise improved when turning on the water tap is most likely because it has a more direct route from tank to steam boiler, pulls water through the pump at a faster rate and has a higher tolerance for air in the stream boiler itself?? Probably talking rubbish but just guessing. It doesn't eliminate it completely however.. Also it's true that when I only turn the brew boiler on which I never tend to do but purely did to test this, there was no groaning whatsoever and the pump sounded as quiet as anything from the first moment. How would I go about checking the solenoid valve you suggested may be the culprit. There were no leaks when I've checked inside and also the steam boiler operates flawlessly.

Thanks again.



Nikko said:


> You say that a) the pump noise gets better when you remove some water from the steam boiler and that b) the noise disappears completely if the steam boiler is switched off.
> 
> Not sure why a) should have anything to do with it at all, and as for b) the only other connection from the steam boiler back to the pump is via the fill solenoid. May be that is the culprit? Another possibility is a split in the HX. Is the steam boiler working OK?
> 
> As regards the NRV, a better design would probably have been to connect the brew HX into the steam boiler from the top so obviating the need for both the NRV and the expansion valve.


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## PaulL (May 5, 2014)

Alas not Christos, it would need someone like DaveC to help from here


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## Nikko (Aug 20, 2014)

christos_geo said:


> Thanks @Nikko, the only reason the pump noise improved when turning on the water tap is most likely because it has a more direct route from tank to steam boiler, pulls water through the pump at a faster rate and has a higher tolerance for air in the stream boiler itself?? Probably talking rubbish but just guessing. It doesn't eliminate it completely however.. Also it's true that when I only turn the brew boiler on which I never tend to do but purely did to test this, there was no groaning whatsoever and the pump sounded as quiet as anything from the first moment. How would I go about checking the solenoid valve you suggested may be the culprit. There were no leaks when I've checked inside and also the steam boiler operates flawlessly.
> 
> Thanks again.


The easiest way to check the steam boiler water line solenoid valve is to see whether the pipe is hot due to escaping steam towards the pump. The pipe and pump should be cold.

With the steam boiler on, if you were to switch the pump on repeatedly, say, every 5 seconds or so, does it make the noise every time?


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## christos_geo (Feb 9, 2016)

Nikko said:


> The easiest way to check the steam boiler water line solenoid valve is to see whether the pipe is hot due to escaping steam towards the pump. The pipe and pump should be cold.
> 
> With the steam boiler on, if you were to switch the pump on repeatedly, say, every 5 seconds or so, does it make the noise every time?


Thank you, will try over the weekend. And no, the noise occurs only after the first and second 5sec draw of water by lifting brew lever after having let the machine warm up for an hour. Some cavitation occurs during warm-ups and during hour gaps between shots allowing that air bubble to get trapped before the pump entry point..


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