Cleaning a steam cleaner

What ho one and all,

I have a Morphy Richards Grime Buster steam cleaner. It does the job, but I have noticed the condensed steam to be 'dirty.'

Thought it was because the steam was cleaning the vinyl, and it probably is but .... In fact the steam is slightly 'dirty.' When I 'flush' the tank with clean water, I get quite a lot of gritty black something and the occasional lump of something soft / black that is like a black clay.

Checked in the tank with my endoscope and everywhere seems to be covered in gunk of some kind. The attached photo, whilst not likely to win Wildlife Photographer of the Year, is what I can see.


What is the stuff? Can it be clean out and if so, how? Some kind of descaler or whatever? Why is it appearing? Is this making the cleaner a tool that is due for the dump?

Toodle pip and thanks

Rex

I'd try kettle descaler, and possibly some Milton afterwards?

I have tried a bit of vinegar in the past but it did not appear to make much difference. On the other hand, I also did not look inside with an endoscope.

Hard water scale usually looks white (ish) but this looks black and the residue that I empty out looks like black sand. What is Milton?

Milton is a weak bleach that people use for babies bottles.
That should kill any bacteria?

I would be tempted to flush with citric acid or vinegar but turn off as it draws in to leave it in the system. I would not be too worried about bleaching it as it runs at least the point of boiling water so any bacteria would be long dead (Unless BBC Coronovirus says otherwise) .

It may start leaking once the scale has been removed though, so be aware.