Provided the section of ...

Provided the section of affected pipe can be isolated temporarily, just simply apply a reasonable volume of compressed air (pressure subject to the grade of the pipe) and you will detect the location of the leak almost instantly.  It ain't rocket science! Depending on the type and size of the leak location, utilize a saddle clamp device that means you don't need to cut the pipe for repairs.

Of course if the rupture is a split than can extend under pressure then cut and shut with gibault's would be recommended as a suitable repair mechanism.