Well, I've never heard of a corporate coupler, but maybe that's going to be the trivia I learn today. Gosh, 1/2" seems to be awfully small for the main water supply line, but I guess you know what you have. Why can you just solder a new ball valve on and go from there? Personally, I would never bury a water line in concrete. Sooner or later there will be leak. There is a constant barrage of questions about how to fix a leak in a concrete slab, and the answer is never cheap or easy. If you could post a picture it might help understand better just what you're up against. Corporate coupler????