Vacuum Box Testing is an effective non-destructive bubble leak testing method used to inspect welding joints at around 11psi (22″ HG). This is a relatively fast test that can be conducted by one person and doesn’t interfere with other fabrication operations. The test uses a box fitted with rubber seals around its open bottom and a plexiglass viewing top cover. The weld section to be inspected is coated with soapy-water solution, and then the Vacuum Box is positioned over the weld. When the Vacuum Box begins pulling a vacuum, the operator will check for any bubbles appearing on the welds. Bubbles indicate leaks in the weld.