What is the best means of access to repair 20 cms diameter hose down wrong to a plasterboard ceiling? ...
Answers: If it is just the stain you are worried something like you can use a good stain blocker primer and consequently repaint. I personally close to Zinsser.
tear it out and put contained by new...that's adjectives you can do otherwise the damage is still here, even if you can't see the water spot(s)