09/25/2026
Just found this inside our heating pipes after a new boiler install a few months ago - normal or not?
So we're mid bathroom refurb and the plumbers had to cut into some old central heating pipework to move things around. When they opened it up, the inside of the copper pipe was coated in this really thick black gunk/scale.
We had a brand new combi boiler installed a few months back, and I was told they did a chemical flush as part of that. So I wasn't expecting the pipes to look like this but also I know nothing about the subject.
I mentioned it to the plumber doing the bathroom work and he seemed pretty concerned, said it looks like the flush didn't really do its job and that running a new boiler with that much crud still in the system isn't great for the pump/heat exchanger long term.
But then I mentioned it to the company that installed the thing and they were like like 'yeah that's pretty normal for an older system, especially if it's never been power flushed before, nothing to stress about'
I have no idea who's right lol.
Anyone who knows heating systems able to weigh in? Is black sludge/scale like this actually a real problem for a new boiler or is it just normal gunk from years of the system running and not worth panicking over? Trying to figure out if I actually need to chase the installer to come back and do a proper flush, or if I'm worrying over nothing?? Thank you for all your help.