the invention provides an improved bubble leak tester , and associated method for performing a leak test and operating the leak tester , to test for leaks in a test part . the apparatus and methods of the invention allow for simple , inexpensive , quick and accurate testing of the test part , provides a visual indication of a leak , and eliminates the part damage and clean - up associated with conventional water immersion tests . further , the apparatus and methods in accordance with the invention control liquid backflow , so that contamination and damage to the device is reduced . in one embodiment in accordance with the invention , a leak tester is provided that is connectable to a reference volume and a test volume for determining the presence of a leak in the test volume . the leak tester comprises a reference port for connection to the reference volume , a test port for connection to the test volume , a bubble chamber connected between the reference port and the test port , and apparatus for selectively controlling flow between the reference port and the bubble chamber and between the test port and the bubble chamber .