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At what point to just replace an E61 mushroom?

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  • At what point to just replace an E61 mushroom?

    I picked up a little BCM Diadema 1GV last night which has seen a pretty hard life in an on-call facility. Not sure it has ever been really serviced.

    Got it working by swapping contacts on the pressure stat, and gave it a back flush which looked pretty clean.

    Then i pulled the mushroom....
    Trigger warning: scale abomination

    Now i should be able to clean out most of the E61 in the head relatively easily, but wondering whether it is worth just replacing the mushroom? After two 20 min soaks in citric acid it has barely budged.

  • #2
    At what point to just replace the mushroom?

    About there, I reckon. That doesn't look like just scale, it seems the base metal of the mushroom is corroding.
    Last edited by Lyrebird; 12 June 2019, 11:42 PM.


    • #3

      Sure does appear to be evidence of galvanic corrosion in progress.
      Would definitely be worth acquiring a replacement Mushroom and a thorough clean of the entire thermo-syphon/HX circuit. I'd also recommend a close inspection of boiler internals to be sure that all is good in there before embarking on regular useage. Maybe a complete overhaul of the entire unit wouldn't be out of the question either...



      • #4
        Surprisingly its not as bad as first feared. Gave it a good soak in citric acid, and a linish with the wire wheel and the base brass looks fine:

        Quite surprised.

        I also had a look in the boiler using a flexible camera and it looks pretty clean. Pulled out the group head and gave it a citric bath too and its come up quite nicely.

        Going to replace a few O-rings and give some good flushes with descaling solution as per the guide on here.


        • #5
          Would be good though if you could now get that mushroom plated with a less reactive metal finish otherwise it's just going to keep repeating the corrosion. It's why they are originally plated with chrome, I believe.

          You might also think about getting your water supply tested and then fit appropriate water filtering to suit. I realise that the original condition was caused with use in another premises, but maybe they use the same water source as you then didn't bother with water filtering to protect the machine.

          Sure does look a lot better than when you started though...



          • #6
            Yeah, i have been eyeing off the ceramic mushroom from Rocket, and the Stainless one from Chris's Coffee. At least with the stainless i can just dump it in Sodium Perc and let it soak.

            Here i have appropriate water for the job. I will use the RO unit for brewing to fill the reservoir. Its not going on mains water, and will be using a coffee cart pump.


            • #7
              Yep, a s/s mushroom should be a durable alternative but not sure about the ceramic one; heard of these being susceptible to accidental breakage and they're not cheap. Mind you, the original should be Ok for a long, long time if the water quality is maintained.

              RO is very good of course but you will need to remineralise in order to bring the TH back up to a level that enhances the coffee shot quality. Easy to do if your RO system can accommodate this for you automatically or just add a pinch of a suitable salt when you refill the reservoir. Magnesium, purportedly, is the best to use as far as enhancing coffee flavour is concerned so maybe a pinch of MgCl2 per water refill would do the trick...