I haven't done it with pipe but I did with trace a wire that went to a light in the yard. I connected a signal generator to the end of the wire from the house and then walked out in the yard and found the location of the wire and where the signal stopped , there was the break.
Not sure how a pipe will work because of the pipe being grounded , the wire of course was insulated.
I used a portable radio (walkman) as the detector.