Abstract: A method and apparatus for detecting a leak in a conduit. The method generally comprises flowing a fluid through a conduit at superatmospheric pressure, placing within the conduit a floatable leak sensor which is responsive to pressure and velocity differentials caused by a leak, moving the leak sensor through the conduit along with the fluid, whereby the leak sensor stops movement through the conduit at the location of a leak. The apparatus comprises a leak sensor casing, a floatable leak sensor mounted within the casing for movement along with fluid through a line of test pipe, and means on the casing to attach casing to the test pipe to allow direct communication between fluid and the test pipe and the floatable leak sensor.