12 full boiler rinses and still lots of sediment - Isomac Mondiale

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by C8H10N4O24teepee »


I have normally had my Mondiale serviced by a store but the quality of work has been hit and miss. So, I've just gone through a descale at home. I've now rinsed the machine a dozen times, the result of the 12th rinse can be seen in the attached photo.

I have a copper boiler and suspect the amount of sediment in the rinse is telling me to replace the boiler. What are your thoughts?
If I do have to replace the boiler I'll get a stainless steel one. Should I also replace the heater element at the same time?
Is it a big job to replace the boiler? Any traps for unsuspecting 'wanna be's'?
What about the copper piping? Is it likely that this too is corroded? Should I be thinking about these too?
Any advice would be very gratefully received.
Thanks very much

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#2: Post by Nunas »

Correct me if I'm wrong, but I thought that the Mondiale is an HX espresso machine with a stainless boiler. So, we need to clarify these points. Perhaps it's changed over the years from copper to stainless.

If it's an HX, from where did you draw the water with the scale, the brew path or the hot water wand? On an HX machine, boiler scale has nothing to do with what you see in the brew path. None of the boiler water goes into the cup; the water travels from the mains/reservoir, through the pump, through the HX tube directly to the group.

If I'm wrong about it being an HX, then please tell us how you did the descaling, including which chemical, how many times you did it, and how long you let it sit in the boiler. Also, please take a more macro photo of the sediment. Rub some between your fingers and tell us what it feels like. Press it on a hard surface with a metal object, such as the back of a spoon; does it crumble, or stay intact.

I would not jump to the conclusion you need a new boiler or piping. I'd first borrow or buy a cheap borescope (e.g., https://www.amazon.ca/gp/product/B07B92KL7J/). Remove a fitting on your boiler and have a good look inside.

As for changing heaters, as long as it heats normally and does not trip a GFCI, your heater is good.

Changing boilers to a new, identical one is not hard to do for someone with good DIY skills, but can be fraught with peril on older machines. When removing fittings, you may find that some of them break off or strip threads. On the other hand, switching out a boiler to a different type (copper to stainless) may require a lot of plumbing changes. You also need to consider the galvanic effect of dissimilar metals. I'm reasonably good at repairing things, but it isn't a project upon which I'd embark.

C8H10N4O24teepee (original poster)

#3: Post by C8H10N4O24teepee (original poster) »

Thanks very much Nunas for your very helpful comments. I had assumed my boiler was copper but, I think you're right: stainless steel. And yes, a heat exchanger.

The water was drawn from the hot water wand. So all of it was boller rather than HX produced. That said, the water comming through the HX and out the group head tastes metalic so I don't expect the HX is in better condition than the boiler.

I'll have to draw some more water but I did play around with the sediment a bit. Much of it is scale that chalks when squeezed between the finger nails. A very small portion of it looks metalic i.e. silver, blue/green copperish (which is why I assumed I had a copper boiler). Some images below are more detailed and a few zoomed in.

I'll drop a photo below of the descaling bottle. I did one run using 50ml of this solution to a full tank of water. I did not overfill the boiler by disconnecting the water probe. I pulled the solution through the HX and group head as well as the HW wand. I let it sit for 20 minutes and did a dozen rineses (turned the machine off, opened the HW valve, drained until empty then opened the group valve before turning the machine on again and filling the boiler).

Thank you again for your helpful suggestions and questions.




Sediment photos

C8H10N4O24teepee (original poster)

#4: Post by C8H10N4O24teepee (original poster) »

I should add too that I removed the mushroom and cleaned the gauze filter. There was scale present in the part of the group head and the mushroom's chrome plating had deteriorated leaving the underlying metal bare in places.

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#5: Post by Nunas »

It sounds like you did everything correctly. You definitely have some scale there. As for the blue/green metallic stuff, that could not be from a stainless boiler, as that coloration is indicative of copper oxide. I'm guessing that it's from the copper piping, which I assume you have in that machine. I'm not familiar with the descaling product you're using, but from the label it appears to be a correct descaling solution. Since it's labelled as "organic", I'm guessing it's likely citric acid based, which is an excellent descaler. You indicate that the machine was previously serviced by a store. Given the quantity of scale you're getting out, it makes me wonder if they descaled it as part of the servicing. It's tough to say what to do next, not being able to get my hands on your machine, but if it were mine, I think I'd give it another descaling, following the instructions on your descaling product. Then flush some more. You might wait a day or two to see if someone here on H-B who has a machine like yours has other suggestions.

C8H10N4O24teepee (original poster)

#6: Post by C8H10N4O24teepee (original poster) »

Sorry for the photo of the descaling solution Nunas, the ingredients weren't clear. I'm attaching a better shot. The label says "Citric Acid < 10% and Glycolic Acid < 10%.

Thank you again for your help.

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#7: Post by Pressino »

Is your Mondiale plumbed in or reservoir supplied? If plumbed in you do you have an in line filter? Some of the stuff emerging from the wand looks like it could have come from your domestic water pipes. Even if your water is low risk for scale this is one reason to use an in line filter or filtered water to supply the reservoir.

C8H10N4O24teepee (original poster)

#8: Post by C8H10N4O24teepee (original poster) replying to Pressino »

It's from the machine's reservoir Pressino, and it does have a small water softener/filter attached to the inlet hose. I had a bench water filter from which I used to fill the machine, now I have an under-sink filter. So, the visible stuff that's coming out is all from the Mondiale, unfortunately.

C8H10N4O24teepee (original poster)

#9: Post by C8H10N4O24teepee (original poster) »

I followed @Nunas advice and descaled again. I got a similar result with lots of sediment as before. Should a descaling solution dissolve the limescale in the boiler or just loosen it from the surface? Is the amount of sediment I am getting given two descales normal?

The quantity of deposit in the spoon is what was expelled from the steam wand on the 10th rinse.

And yes, @Nunas, you were completly correct. I have a stainless steel boiler :-)

Thanks folks

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#10: Post by Nunas »

Gosh, that's a lot of grit from a machine that has been repeatedly descaled and flushed. The answer to your question is, "both". Descaling solutions are an acid base (yours is citric acid, which is excellent). Acid dissolves lime scale, but the way it is usually used, contact is not long enough to dissolve it all. We have very hard water here and folks without water softeners routinely use pure citric acid powder, such as Lemishine, in their dishwashers and clothes washers. That said, we earlier discussed the nature of the crud you're finding. Some was clearly lime scale (it crushed and is generally a shade of white/tan). Your latest photos show quite a lot of very dark flakes. I'm at a loss to understand what these are.

Citric acid is excellent for stainless steel. Often it is used to passivate stainless boilers; it does this by removing introduced iron. We used to use it to clean the 500-gallon stainless water tanks on our motor yacht, so they would not rust. Also, it won't harm copper. If it were me, I'd try this. Put the expelled crud in a glass container and add some of your descaling solution to it. Leave it for quite a while, even overnight. We need to see if it will dissolve whatever that crud is. If it does, then I'd do another descaling and leave it much longer than recommended. Anecdote. Many years ago, my dad's retirement business was small appliance repair. Sometimes he'd get coffee machines that were so choked with scale that water would barely pass through them. He'd put 50/50 household vinegar and water solution in them, run the pump for a while, then pull the plug and leave it overnight. It was alarming to see how much crud was expelled the next day. BTW, don't use vinegar, as I don't think it's as safe on stainless as citric acid.