The Polyweld POLYVIEWER vacuum tester is available for short and long-term hire from Polyweld Machinery. The POLYVIEWER vacuum tester is a weld testing instrument for assessing the weld integrity of overlap weld seams on geomembrane liner (such as HDPE). The purpose-built viewing dome is attached to a backpack-style vacuum unit, and the dome is placed over a section of weld that has been sprayed with soapy water. Once the vacuum is applied, the presence of bubbles at the weld seam can indicate holes or flaws in the weld. Vacuum testing is a widely used quality assurance method for assessing welds in plastic membranes lining ponds and dams.