Bubble Leak Testing or Bubble Emission Testing is a method that detects leaks visually and identified by emissions of bubbles when testing specimens are submerged into water.
Bubble emission test, or submersion leak test is the test for underwater immersion, or "dunking test" is a method of detecting and finding leaks in the specimen via the release of bubbles.
There are two methods to carry out bubble emission tests: Pressurized (ASTM F2096) and Vacuum (ASTM D3078). The pressurized method involves the specimen being tested is pressed over the ambient pressure. According to the altitude at which the test is conducted the gauge pressure could be at the highest level that the test will allow.
The test specimen can be pressurized via sealing or through tubes attached to the test sample while the test for leaks in bubbles is carried out. The benefit of pressurizing the piece is improved leak detection because of the extra pressure applied to the test sample.
The downside is that the test is more complicated as compared to the Vacuum Test. Another drawback to this type of test Pressurized Test can be that some test specimens are not able to withstand greater pressures and may explode or be damaged by the high pressure inside.
But the leak testing using pressurized method might be the right option in light of tests needs. Vacuum test method, on the contrary, doesn't require additional pressure on the test sample, and could be more beneficial because of the ease of testing that it provides over the pressurized test method.