My main machine had been working noticeably worse over the last few months.
It felt like the machine just wasn't making it though coffee at the correct grind size.

My sister wanted to change the pump.
Then I had a think: When was the last time I remember descaling?...and I couldn't remember.

Descaler in, shower screen off, brown sludge out.
Left it overnight, flushed it through in the morning and...wow, my coffee machine is working properly again.

And the tasty local Rwanda is drinking very nicely indeed.