In this work we present a new in-pipe leak detection robot, the MIT Leak Detector. The system performs autonomous leak detection in gas pipes in a reliable and robust fashion. Detection in based on the presence of a pressure gradient in the neighborhood of the leak. As the MIT Leak Detector travels through pipes, it picks up the pressure gradient in case of leaks via a carefully designed detector. In this work we demonstrate the performance of the system in a lab setup, which consists of 100mm ID pipes containing pressurized air.