The concept of a compression gasket to form an engineered seal is an accepted industry practice used for years in the installation and joining of sewer pipes. Even though the engineering society understands that the best long-term solution is an engineered gasket seal, one must select the proper gasket, which is designed for CIPP applications.
The use of a hydrophilic rope or belt shaped material commonly used in a cold-concrete-joint is not suitable for CIPP renewal works. Those who have attempted to use this type of seal will appreciate the challenges of effectively securing a penannular or non-monolithic gasket to the inside of a pipe. Some of the problems that occur with this method are that gluing anything into a wet and greasy sewer pipe is a challenge in itself. If the gasket falls over during insertion of the liner, the result is a large bump at the invert of the pipe; or the contractor simply doesn’t install the problematic gasket as required. Even if one were to assume the gasket could remain in-place as the liner is inserted, the ends of the gasket would have to abut or overlap.
The belt type gasket creates a significant opportunity for separation or a gap in the gasket resulting in continued leakage where hydraulic loading is present. Furthermore, these belt shaped gaskets are fairly narrow, producing an insignificant sealing surface. They are also quite bulky in thickness, reducing the cross section of the pipe which may hinder the insertion of robotic cutters, maintenance and lateral connection lining equipment.
In order to correct these deficiencies, a considerable amount of research and development has been initiated to produce a truly engineered mechanical end seal which is simple to install, is effectively secured to the inside of the pipe, and has a significant sealing surface and a low profile that maximises the cross section of the pipe opening.