Removed the boiler from my Gaggia Classic and it was a humbling experience to learn just how much scale can build up even on RO water.
Ultimately wasn’t able to get the boiler looking squeaky even after 2 hours of sitting in descale solution. Is that probably fine? I just rinsed and brushed it until I didn’t see any more visible scale flakes coming off. Flow is back to normal as far as I can tell.
About 7 years! Some on RO water, some without. I was a horrible owner but came around in the last 2-3 years with better maintenance.