Recently had my plumber round to connect up the overflow pipe for the boiler he installed last year (the pipe needed to go through the kitchen, and I was planning on installing a new one, which I now am), so in the meantime he left it running through the bathroom overflow.
He's drilled a hole in the outside wall, and the overflow terminates in a bit of 15mm copper sticking out of that. It seems to me that I ought to seal the hole with something
- but what?
Ben