These types of stituations are always tough to find and expensive to repair. I would check with your local plumbing inspector or city building department. Talk to the inspector personally and explain the situation. Ask for recommendations for people who have done this type of work before. Personally, I like the camera method for the larger pipe. You can locate the break most of the time. If you do find it, you can locate it exactly with the radiolocator at the end of the cable. It is expensive. Write us again and let us know how you come out.