I took a look inside the boiler. I'm sure it could look better, but it doesn't look that bad, does it?


I siphoned the boiler and hx tubes, each time there was just a small piece of scale:





But when I turn machine on and the boiler reaches its nominal pressure and I start the water pump, the water contains a lot of scale:

homeburrero wrote: I think you could get away with removing a fitting like the anti-vac valve and doing repeated descaling and rinsing of the boiler, with strong spray and siphoning until its clean of all loosened scale, maybe remove the pressurestat and make sure that pipe is clear, then finish up with a final conventional descale or two. Others with professional experience (Stefano or JRising for example) would know best about that.

So my next steps are:
1. descale boiler with some agent. Any recommendations? Would citric acid be enough or should I go with some stronger e.g. Dezcal? I'm worried about not able to rinse it properly. I should do this with machine being off and cold, right?
2. use conventional descale. Again, should I use some stronger agent like Dezcal or citric acid should be enough? Any particular method to follow? I saw a pretty good tutorial by WLL, is it ok? Should I descale above the water line by removing a little the water sensor?

I need some advice. So far I descale boiler 3 times with citric acid (2 tsp/l, 12h + 12h + 24h). Water from descale was greenish only from first descale. Each time there is less and less clogs siphoned out. Should I continue descaling boiler with stronger solution and/or longer times? Or should I take a chance and run a conventional descale (boiler and HX) hoping that heated solution will get rid of the remaining clogs in boiler?

I had a recent scale issue and the tech from Chris' Coffee advised me that they will use a stronger solution, up to a 1/2 cup per reservoir, for stubborn issues. I think you can pretty heavily increase your concentration.

If you really are using 2 tsp (teaspoons) per liter you are using a very weak solution. 2 tablespoons per liter is more typical, and some have advised as strong as 4 tablespoons per liter, which would be in the ballpark of 1/2 cup of citric acid in a 2 liter reservoir. (Some discussion is here: Citric acid to water solution for descale ) And it does work faster if heated.

One very experienced machine restorer switches between citric and commercial sulfamic descalers when doing tough jobs. But that is for disassembling and acid bath. (see Faema E61 Legend Scale )

It's possible that you have layers of calcium sulfate (gypsum) deposits mixed with carbonate scale. The calcium sulfate might break loose but would not dissolve in any typical descaling solution even if mixed very strong. Try pulverizing some of those scale clogs that come out, and then try giving them a good soak in a glass of hot strong citric acid solution. If they don't dissolve that might be what you are dealing with.

homeburrero wrote:It's possible that you have layers of calcium sulfate (gypsum) deposits mixed with carbonate scale.

Seems like my problem. I soaked these clogs in strong citric acid and vinegar, neither dissolved them. Is there anything I can do remove it? Or is the never-ending fill-drain of the boiler the only way?

edit: however I will keep these clogs in solution for couple of hours more just to make sure they will not dissolve

edit: after 12 hours clogs were not dissolved

Have you made any progress on your machine? I am having similar issues with my Appartamento:

Low Rocket Appartamento Grouphead Temperature

kulka wrote: I soaked these clogs in strong citric acid and vinegar, neither dissolved them. Is there anything I can do remove it? Or is the never-ending fill-drain of the boiler the only way?

If calcium build up is bad, use a wire brush or some "aircraft cable in a drill" to break it down into debris that can be flushed away, then descale to see if it gets anything so you know if there's any left.

It does sound like you have a calcium sulfate problem, which is more likely in steam boilers than brew or HX boilers because of the concentration of calcium and sulfate ions in the steam boiler as a result of steam wand use. There are no easy chemical treatments for sulfate scale. Normal acid descalers are useless, and extreme methods (sodium hydroxide, HCl, and Sulfuric) that might work are just too dangerous for you and the machine. In theory an EDTA + potassium carbonate descaler might work but I don't find any commercial espresso descaling products that use that.

Best bet is mechanical cleaning and vigorous flushing as JRising advised. If you can switch to a water that is completely free of calcium and sulfate then I think you can expect the existing calcium sulfate scale to slowly dissolve over time. Here's an old thread from rpavlis that has some interesting sulfate scale info: The chemistry of scale in espresso machine boilers [FAQ] .

So I descaled boiler with even stronger solution and flushed the boiler vigorously several times more. Still there were some minor clogs, probably calcium sulfate as you suggested, but I decided to give it a try anyway. I did some search over forum to see that these may be produced by BWT-like filters and/or not flushing boiler for a very long time. I decide to keep BWT, but will flush boiler like every two or three weeks. Anyway, I then ran with conventional descale. At first, the was some clog choking the system, but eventually it dissolved in the solution. I flushed the system with couple of litres of clear water, and flushed the boiler siphoning it for the last time. Then it was time to see how things are going. Water from hot-water wand and from the group - exceptional and sweet taste (Mg+ from BWT system). The group reaches 208F without any problem now, and there is no issue with the water flow. I'm now enjoying my cup of coffee for the very first time since like a year or more.

I'd like to thank all of you who contributed to this thread!