A copper or other conductive wire is laid under the overlap edge before the bead goes on; afterward a high-voltage probe is run along the seam, and a spark jumps wherever the bead has a hole. It is used where a vacuum box cannot seal, such as pipe boots, corners and steep details. The wire must be continuous and grounded for the test to mean anything.
Heard on the job
Lay the wire before you weld the boot, or there's no way to spark test it afterward.
Also heard as
- spark testing
- holiday test
Related terms
Extrusion weld
Geomembrane seam made by laying a bead of molten polymer along the edge of an overlap, used for patches and details.
Boot
Field-built geomembrane sleeve that seals a liner around a pipe or other penetration.
Vacuum box
Clear-topped box pulled to a vacuum over soapy geomembrane so leaks in seams and patches show up as bubbles.