Should I replace or ignore this?

[Kmurphy]

I’m replacing a ceiling and I’ve uncovered some pipe work. There’s been no issues with the plumbing and no leaks, but they look pretty appalling. Maybe it’s just old flux, but having seen them, should I DO anything?

 

[Burnerman]

It's harmless but looks horrible......polish the grot away with wire wool and observe!
John

 

[Kmurphy]

If I clean it up and there is a teeny weeny leak, what’s the best way to pick that up? But if tissue wrap? I’m burying it all again in a weekend or two

 

[Burnerman]

Polishing the crap away won’t cause any leak......but if there is one, it’s time for action!
Any leak will quickly show on kitchen paper or whatever.
John