Have you got enough room to get a dish of some sort under it?
If you can, then do so and empty it as required; I know it sounds stupid
and it's not a fix, but it will stop the damp damage constantly being
renewed while the experts have a think.
Is the leak from the end of a fitting, connector, or coupler?
Is it soldered, or does it have a bosy with nuts, or has it somehow
appeared in a length of virgin pipe.
Is the pipe 15mm, about 1/2" across, or 22mm (3/4") across?
Answers in your next post, please ;-)