Abstract: A testing device is disclosed for testing a drainage system for leaks, the testing device being selectively connectible to a source of fluid flow. The testing device includes an elongate tubular member having a first and a second end. The tubular member is disposed in fluid tight series communication between the drainage system and the drain. The tubular member defines an internal annular ledge which is disposed between the first and the second end of the tubular member. The tubular member also defines a first lateral hole which is disposed longitudinally away from the ledge. A removable blocking disc sealingly engages the ledge for temporarily preventing flow of fluid from the drainage system to the drain during the testing of the system for leaks. A closure is disposed within an access opening for permitting access to and removal therethrough of the blocking disc from the tubular member subsequent to the testing of the system after the removal of the closure from the access opening.