Could you get a slightly larger pipe around that pipe then fill the wall with plaster and the gap between rad pipe and newly added pipe with flexible filler. If you found a flexible enough plastic pipe and cut a slot in it you might get it over the rad pipe.
Could you get a slightly larger pipe around that pipe then fill the wall with plaster and the gap between rad pipe and newly added pipe with flexible filler. If you found a flexible enough plastic pipe and cut a slot in it you might get it over the rad pipe.