E61 mushroom scale or corrosion? What should I do?

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

#1: Post by Fercho »

Hi everyone,

My Lelit Bianca has 3 years, and for the past year it's been plumbed in and using a BWT Smart Bestmax 25 filter. The first two years I used the Lelit water softener with a regular 6 months replacement.

A few days ago I took the mushroom off and noticed flaking and corrosion on the mushroom. I don't know if scale is present or not (don't know how it looks like).

I've read through the forum and it seems the consensus is to leave the mushroom up to the thread in white vinegar for an hour, and then try to use a green scrubbie to remove as much of the plating as possible. Is this the best way still? Or is there a new recommended procedure?

Also, any other recommendation to avoid further corrosion?


Team HB

#2: Post by JRising »

Looks like you're doing fine. You could have started with a brass-bristle brush to reduce the amount of work the vinegar would have to do, but the soaking will do it.
Do exactly what you have just done! :D

Finish off with the green scrubbie and don't worry about being able to see the brass.


#3: Post by Bluenoser »

I had a similar experience with my mushroom, after using what I thought was good water (RO + TWW). I since have halved my TWW concentration from their recommendation.

But one person told me that plated mushrooms have a real tendency to scale. I have a Profitec 500 and they since switched to a stainless mushroom. For the cost, I'd replace yours with a stainless, if you can get one. Much 'hardier' than the brass plated.

Fercho (original poster)

#4: Post by Fercho (original poster) »

Amazing! Thanks for your replies. Will look for a stainless mushroom.

Team HB

#5: Post by JRising »

The scale building up on the mushroom isn't a problem, it's the evidence of a problem.
Scale built up on the mushroom is a fast and easy way to judge that there's scale building up in the brew circuit, so that you know you have to descale the brew circuit and improve your water.

Switching to a stainless or ceramic mushroom will just make you have to lift the brew valve to determine the scale level in the brew circuit.


#6: Post by WWWired »

Hi Fercho :)

Excellent post and brilliant replies by JRising and Bluenoser :)

No question your goal is to avoid at all costs ingesting Brass, Aluminum, Lead, Chromium, or Copper atoms. None of these are good for your organs or Brain, and metal atoms cross the blood-brain barrier without any resistance by your body, where the atoms then get deposited in the brain causing health issues over time.

This type of issue is an excellent primer for anyone who owns a high quality espresso machine why annual or biennial (every two years) maintenance is the minimum that should be considered as a goal for inspection of the surfaces that come in contact with the food and beverages we consume.

The Metal Mystery:
There appears often to be a lot of discussion about Metal Corrosion. Much is said against platings such Chrome and Nickel etc. but it might surprise many to learn the truth that all metals are safe . . . and dangerous. The only difference is Corrosion. Catching Corrosion in the act and putting an end to it (as JRising wisely mentioned above in suggesting addressing the cause, not the symptom), is very important.

As an example, Stainless Steel, or CRES, (Corrosion-Resistant-Steel) is a steel alloy that contains a minimum of 11% chromium content by weight . . . that's right, the thing that puts the Chrome in Chrome-plating. Many of our fittings and other components in our wonderful higher quality espresso machines contain Stainless Steel components, Boilers and other parts. It might also be worth considering that several alloys of stainless steel include substantial amounts of nickel to inhibit corrosion . . . there's that word again . . . "corrosion." So why is Corrosion so bad?

Corrosion can cause metal atoms to be released from the surfaces of our machine components that come in contact with the fluids and foods we consume. Ingesting too much of these atoms has some health consequences that should be avoided if possible.

The Magic of Citric Acid
Yep, some say Citric Acid is bad and promotes corrosion. This can be true of some metal platings. But . . . and this is a very important point . . . Citric Acid is used in a process called "Passivation" for Stainless Steel and even other metals. What is Passivation?

Passivation is the process of using a chemical oxidizing agent to strip free iron from the surface of a metal component while adding a protective oxide layer. And here's the myth-busting truth, Citric Acid is the magic ingredient. Used in "Passivating" medical stainless steel, Citric Acid is an invaluable tool for creating safe for human metals. It provides resistance to corrosion and as most coffee culture folks know, it does one heckuva job of cleaning our beloved espresso machines of any mineral scale buildups that are often involved in that nasty "Corrosion" thingee.

When Corrosion is spotted, it is definitely worth addressing immediately. Get the root cause as JRising mentions, and try to use metals that are high quality and less corrosion vulnerable as Bluenoser stated above as well.

And finally, here's the Home-Barista sites brilliant guild on Espresso Machine Cleaning Why, How, and When

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#7: Post by borrik »

Is this machine is 3yo?? Hard to believe the mushroom and even the cap looks terrible :shock: looks like very agressive water or cleaning solution. Were all the separated coating? Was it dissolved or collected inside the the group channels? Maybe it's worth to check dispersion screw...


#8: Post by Pressino »

It does look like corrosion rather than limescale. I'd be concerned about high chloride levels in the water supply. Bestmax and other similar filters don't do anything to significantly reduce chloride levels. If you have high chloride levels, the best ways to deal with that are: 1) Use distilled water reconsitituted with non-scaling minerals (see the Water forum here for details); 2) use bottled water with known "safe" mineral content and low chloride content; or 3) use reverse osmosis and reconstitute the water as per #1 above.

The advice about replacing the chromed mushroom for SS is fine, but if chloride is high, it will corrode just about any metal, plated or not.

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#9: Post by stefano65 »

Apart from the price of the ceramic ones (which we do stock as well)
the concern I've seen so far in machines coming in for repairs is that:
they get stuck in the grouphead (regardless if is ceramic or not) in the lower area by the internal o-ring,
but some of them are cracked by previously trying to remove them or from the possibly over tihteningh from assembly,
they can also crack during removal,
if you decide to get for a ceramic one
I strongly suggest to have the chamber completely clean and to use appropriate grease on the o-ring, then periodically removing it for inspection and re-greasing.
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.
★ Helpful

Fercho (original poster)

#10: Post by Fercho (original poster) »

Thanks for all the responses, specially for the very informative post by WWWired!

I bought a water test kit (https://www.amazon.com/dp/B08663FGJG?ps ... ct_details) to see what I'm dealing with. I have a whole house filter system before the Bestmax that supposedly removes chlorine, but to be honest I haven't tested.

Also, how I'm supposed to use citric acid?