This is an un-restrained joint system which is used for the installation of long runs of buried pipe lines with only few accessories. Integral socket and spigot ends are joined together as in fig-1 or two spigot ends are joined with a double bell coupling as in fig-2. In this joint system, the hydraulic sealing is performed by elastomeric rubber rings, installed in circumferential groove on the integral socket and the coupling. Rubber rings are available in different materials like NBR, Neoprene and EPDM to suit the individual application. The installation in very fast and easy. Since it allows angular deflection, changes of gradient or curve can be easily accommodated and it is also called flexible joint. Concrete thrust blocks are required at the directional changes, as it cannot accommodate longitudinal Forces.