I would like to know if there was any suitable technique or equipment to detect and determine the exact location of the leakage in underground piping without the necessity to digging. masoud

masoud, Helium leak detection systems have been around for a long time. To use such a system, you must have access to all of the area above the underground piping and the piping leak point can be detected only to a depth limit of about 15 feet. According to the vendors, the leak point can be detected and located through asphalt paving See this website: http://www.medivactech.com/Tanks%20and%20Pipes.htm Several companies offer this service..... Other than helieum leak testing, you may get some limited results with robotic pipe crawlers, but you must have a clear liquid to work with... My opinion only MJC