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Duetto II draining water.

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My Duetto II have started to empty the internal watertank and fill up the waste tray. It takes around 8-10 hours before the watertank is empty.

I replaced the OPV around 2 years ago because of a steam leakage. (all the upside down cups on the top tray was wet inside). The steam leakage problem is gone but the answer from bellerista is to change the OPV again.

I don`t understand. Do i need to replace the OPV every second year or is it another solution.

 

Kind regards

T. Andersen

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Is this the OPV on the brew water circuit? Problem happening when machine hot or cold?

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Are you in a hard water area...where do you live?


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The problem is only in standby, when steam switch is on. Turning of steam, and the problem is gone. I live in Norway, and the water here is not hard.

 

Regards

T. Andersen

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It sounds like the vacuum breaker valve is leaking. The inside of your machine should look like exactly this, open the top and check that it is and that there is no plastic pipe on component 1 and 2.

 

1. Is the safety valve, if this leaks if this leaks then the boiler will keep autofilling and use water from the tank, cups on tray will be damp and there may be water below the machine, unless the leak is very slow.

2. Is the vacuum breaker, if this leaks then the boiler will keep autofilling and use water from the tank, cups on tray will be damp and there may be water below the machine, unless the leak is very slow.

 

Without any plastic tubes on these leading to the drip tray, neither component leaking will cause the drip tray to fill up.

 

3 is the expansion valve (what you call the OPV). If this leaks, then it will fill up the tray, unless the plastic pipe is routed to the water tank, some MKII machines had 2 pipes in the water tank, one coming from the expansion valve! See second photo. Some later MKII models did route the expansion valve output to the drip tray and may have had a tube on component 2 (Vacuum breaker). You need to find out exactly which version yours is, to make sure you identify the correct component leaking water into the drip tray. As you said.

 

The problem is only in standby, when steam switch is on. Turning of steam, and the problem is gone. I live in Norway, and the water here is not hard.

 

I really doesn't sound like the expansion valve, as that really only deals with expansion of cold water entering the brew boiler after a shot being reheated....if the steam off solves the problem, then logically it must be either component 1 or 2. Uplaod a photo of your machine with the lid off and try to include the water pipes/tank as well.

 

dmk2.jpg

 

dmkii water.jpg


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Thank`s for your reply. My much older Duetto looks like this. last time, i replaced the part showing by the arrow.

20180415_091052.jpg

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Just thinking out loud...

If the OPV wasn't seating properly, water could backsyphon from the tank into the brew lines. It could then run out through the solenoid valve into the drip tray. This would happen whether the machine is on or off. A simple test would be to raise the return pipes above the level of water in the tank and see if it still happens.


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Just thinking out loud...

If the OPV wasn't seating properly, water could backsyphon from the tank into the brew lines. It could then run out through the solenoid valve into the drip tray. This would happen whether the machine is on or off. A simple test would be to raise the return pipes above the level of water in the tank and see if it still happens.

 

It's an interesting thought but it's not how the system works at all on the Duetto II. The drain from the expansion valve (OPV) feeds back to the tank using the second pipe (two pipes in the tank on that model). The water that comes from the expansion valve is just the amount of water that expands when the brew boiler is used, cold water enters and then expands dues to heating. The solenoid valve is for controlling where the water goes e.g. to the brew water circuit, or to fill the service boiler.

 

Thank`s for your reply. My much older Duetto looks like this. last time, i replaced the part showing by the arrow.

 

The photo I took was of a Duetto II (may 2009) about 9 years ago. The arrow part as someone has already identified is a safety valve. The condition of the machine looks as if that and/or the vacuum breaker (and possibly other components) has been leaking unnoticed for years. This does show the importance of a top cover off inspection annually...it's only 4 screws!

 

I cannot see the Vacuum breaker where it should be, so I don't know if it's a modification done in a later production run (or a local mod) to move it, but unfortunately your photo doesn't show the entire top area of the machine (as mine did)


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It's an interesting thought but it's not how the system works at all on the Duetto II. The drain from the expansion valve (OPV) feeds back to the tank using the second pipe (two pipes in the tank on that model). The water that comes from the expansion valve is just the amount of water that expands when the brew boiler is used, cold water enters and then expands dues to heating. The solenoid valve is for controlling where the water goes e.g. to the brew water circuit, or to fill the service boiler. ]

 

Thanks, you are likely to be right but I was thinking of the device that regulates the brew circuit pressure during extraction (which is attached to the other pipe going to the tank) and the solenoid valve that releases pressure from the group head.

Again, it was just a thought.


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The brew circuit pressure relief valve looks to be going to the drip tray so is a suspect. Is the vacuum breaker also going to the drip tray? Easy to check and if so another suspect.

 

With such a big flow going to the drip tray you should be able to see where it is coming from. If from the pressure relief valve you should see increased flow when the pump is running.

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It's an interesting thought but it's not how the system works at all on the Duetto II. The drain from the expansion valve (OPV) feeds back to the tank using the second pipe (two pipes in the tank on that model). The water that comes from the expansion valve is just the amount of water that expands when the brew boiler is used, cold water enters and then expands dues to heating. The solenoid valve is for controlling where the water goes e.g. to the brew water circuit, or to fill the service boiler. ]

 

Thanks, you are likely to be right but I was thinking of the device that regulates the brew circuit pressure during extraction (which is attached to the other pipe going to the tank) and the solenoid valve that releases pressure from the group head.

Again, it was just a thought.

 

The Duetto II has a rotary pump...the rotary pumps have a small valve system built in, it's called a "balanced bypass". This basically recirculates excess water back to the inlet of the pump and it's all within the (Fluid-O-Tech) pump body. No water is released anywhere because of this, but of course iof the pump is run against a blind filter for long enough the whole thing will heat up and eventually damage the bypass system, then destroy the pump...but it takes a surprisingly long time!

 

The device your thinking off often known as the "OPV", it's proper name is the "expansion valve". It's job in a dual boiler is not to regulate brew pressure and it's usually set to 12 or 12.5 bar this is well above the normal 9-10 bar brew pressure generated by the rotary pump when properly adjusted. Unless there is a fault or someone has adjusted it wrongly, thinking they will adjust brew pressure. Perversely if your rotary is set too too high a brew pressure adjusting the expansion valve will lower brew pressure, but this is actually incorrect to do and will often cause problems due hydraulic circuit design in many rotary pumped machines. The Duetto MKII should (unless there were local modifications, or modifications during the MKII production run) vent liquid from the expansion valve into the tank. It was on later Duetto models they finally took on board my recommendation to vent the expansion valve to the drip tray.

 

The expansion valves function is to prevent the expansion of water in the brew boiler (e.g. when cooler water enters during a shot) from splitting pipes, the boiler or damaging fittings. Unlike a steam boiler which has some head-space, the brew boiler does not and water is almost incompressible (for all practical purposes). This expansion can generate tremendous pressure! In a rotary pumped machine, that is really it's only function BUT in a vibration pump machine it is also used to regulate brew pressure. It does this by being set to dump water as soon as the pressure exceeds say 9.5 bar, in this case it cannot be vented to the drip tray, but always back to the tank as far too much water would fill the tray.

 

Lastly the valve that releases pressure from the group head is part of 3 valves in the E61 group, it is the lowest valve and called the "vent valve". in the duetto this is mechanically operated by a cam attached to the E61 lever, which when lowered depresses a pin attached to the "pre infusion valve" (which is set to 4 bar) and this also opens the "vent valve". The "vent valve" is usually set to around 13.5 bar so it can never open during normal brew pressures. it's not set higher than 13.5 because this would make the E61 lever unnecessarily stiff and cause premature wear of internal E61 components. The last valve in the group is the top group valve, this can leak and cause water to either evaporate off the group head, or if bad enough fill the tray. This vale is positively closed by a spring and one directional, so increasing brew circuit pressure only closes it tighter, until it's pin is pushed upwards by the cam attached to the E61 group lever.

 

It's all quite simple, but a great mechanical design from the 60s and still works great today..If you want to know more:

 

http://coffeetime.wikidot.com/search:site/q/e61

 

What I really would like to see is better photos of his machine similar to those I put up and then I can tell for sure if there have been mods, especially the area behind and just aove the drip tray (with the drip tray removed). I do think there is one difference as I can't see a vaccum brealer where it should be, but they may have put it on a tube away from the boiler?


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I've had to replace the expansion valve (part 3 on DaveC's diagram) on my Duetto several times as it was filling the tray. It's actually only the rubber pad inside that had become hard and compressed but I was unable to find it in the UK anywhere (you can in the US: https://www.chriscoffee.com/Expansion-Valve-Replacement-Seat-p/8f194v.htm) and had to replace the whole thing (which is not too expensive and easy enough: just take the whole T-shaped pipe assembly off by undoing the nuts).

 

This is the part: https://www.bellabarista.co.uk/izzo-over-pressure-valve-fe304.html

 

Unfortunately they were out of stock for many months at one point so I had to find it elsewhere. I now keep a couple of spares!

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I've had to replace the expansion valve (part 3 on DaveC's diagram) on my Duetto several times as it was filling the tray. It's actually only the rubber pad inside that had become hard and compressed but I was unable to find it in the UK anywhere (you can in the US: https://www.chriscoffee.com/Expansion-Valve-Replacement-Seat-p/8f194v.htm) and had to replace the whole thing (which is not too expensive and easy enough: just take the whole T-shaped pipe assembly off by undoing the nuts).

 

This is the part: https://www.bellabarista.co.uk/izzo-over-pressure-valve-fe304.html

 

Unfortunately they were out of stock for many months at one point so I had to find it elsewhere. I now keep a couple of spares!

 

Is your Duetto a MKII? You have to remember OP has a MKII, and although the OP has not posted the photos I actually asked for, unless there was a mid production run change (or local mod), his expansion valve vents back to the tank! The other thing he said was that this only happens when the steam boiler is on, which additionally excludes the expansion valve as that's only to deal with water expansion due to brew boiler heating.

 

Of course unless the OP actually responds with better information, he won't get his problem accurately diagnosed.


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Is your Duetto a MKII? You have to remember OP has a MKII, and although the OP has not posted the photos I actually asked for, unless there was a mid production run change (or local mod), his expansion valve vents back to the tank! The other thing he said was that this only happens when the steam boiler is on, which additionally excludes the expansion valve as that's only to deal with water expansion due to brew boiler heating.

 

Of course unless the OP actually responds with better information, he won't get his problem accurately diagnosed.

 

It is a little confusing that the model version specifics have both a model number and a revision mark! I should have read the other responses more carefully, though hopefully my reply will be useful for future searchers trying to diagnose a full drip tray. Mine was sold by Bella Barista as the Alex Duetto II Mark III though all the manuals and paperwork just call it an Alex Duetto II, (and it was of course chosen in large part because of your excellent "Duetto II closer look" pdf).

 

It would be worth checking whether the steam switch effect is just coincidence or not. When my expansion valve started to leak it wasn't continuous so a quick test may seem like switching off the steam boiler corrected it.

 

As you say a photo from OP would be useful to establish the exact configuration of his model.

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It is a little confusing that the model version specifics have both a model number and a revision mark! I should have read the other responses more carefully, though hopefully my reply will be useful for future searchers trying to diagnose a full drip tray. Mine was sold by Bella Barista as the Alex Duetto II Mark III though all the manuals and paperwork just call it an Alex Duetto II, (and it was of course chosen in large part because of your excellent "Duetto II closer look" pdf).

 

 

It would be worth checking whether the steam switch effect is just coincidence or not. When my expansion valve started to leak it wasn't continuous so a quick test may seem like switching off the steam boiler corrected it.

 

As you say a photo from OP would be useful to establish the exact configuration of his model.

 

Thank you that closer look was many years ago now and when I did the original top level design for the Duetto MK1 and testing, it was a few years before that.

 

 

  • If you have a MKIII then your expansion valve drains into the drip tray...but I doubt the OP valve does with a MKII.
  • He did check with the steam off and it didn't do it, hence why I think it's is unlikely to be the expansion valve

 

It is a shame that he didn't put up a better photo of what I asked for in the first place . I even gave examples with my photos of a MKII machine like his. I am also a bit worried that someone may have modified it and removed the vacuum breaker from the machine, because I can't see it where it should be, but the photo doesn't show all of the top?

 

I'm just going to wait to see if he posts again and gives better information....without it I can't help him and he might as well try trial and error, or take it to a local repair shop.


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For the sake of accuracy, what some here mistakenly call "expansion" valve is actually a pressure relief valve. OPV will also do. In the English world it is common to name valves according to the function they perform, i.e. diverting valve diverts, mixing valve mixes, pressure relief valves relieves pressure. And expansion valves expand - they are used in refrigeration.

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