None of the other available methods for testing manhole integrity are as quick, easy or accurate as vacuum testing.
Vacuum Testing establishes a differential pressure between the inside and outside of the manhole structure by reducing the internal pressure of the manhole. This simulates the same differential condition as having increased pressure on the outside of the manhole, which is exactly the condition that we want to ensure that it can withstand once it is put into service. As a vacuum is drawn on the manhole each joint is pulled tighter together and the flexible connectors are stretched inward, providing realistic simulation of external groundwater head pressure This provides for a far more dynamic test of the structure than a simple water exfiltration test.
If the manhole fails the test, leaks can be easily located by spraying water on the exterior while still drawing a vacuum, and looking for areas that dry quickly on the outside or wet areas inside the manhole. Once the leak is identified repairs can be made by applying a quick setting patching material. By making the repair while continuing to draw a vacuum the patching material is pulled into the wall of the structure creating a far more effective seal.
<%=company%>, Po Box 301, Millford, NH 03055. Tel: 800-626-2180; Fax: 603-673-7271.