A method of detecting a leak source within a tank includes coupling a first seal member to an external surface of the tank around an external leak location and coupling a second seal member to the external surface around a perimeter of the first seal member to define a gap between the first seal member and the second seal member. The method also includes coupling a sealing membrane to the first and second seal members such that a first cavity is at least partially defined within the perimeter of the first seal member and such that a second cavity is at least partially defined between the first seal member and the second seal member. The gap at least partially defines the second cavity. The method further includes applying a vacuum to the second cavity and injecting a detectable gas into the first cavity.