fig4 and in fig5 standard commercially available straight pipe is commonly sold and has the diameter sizes required in nipples 16 nipples 16 are also provided with a bevel on both ends 21 see fig5 and the provision of such bevels is also readily available commercially the suggested bevel is about 15 over one inch referring to fig8 the maximum length of the nipple 16 is calculated such that it is less than the distance between the sloping shoulders 20 of the two opposing bells 12 so that as indicated in fig8 if the nipple is over inserted into the one bell during installation such that a bevelled end 21 thereof contacts the inside surface of sloping shoulder 20 the other end of the nipple will not contact the opposing shoulder thus the longitudinal load will still be borne between bell mouth faces 23 and nipple 16 will not be broken or deformed further the nipple is provided with a minimum length also illustrated in fig8 so that if the nipple is over inserted to the left as illustrated in fig8 the nipple must be long enough so that its unbevelled outer surface extends beyond gasket 14 in opposing bell 20 this ensures a fluid tight seal even though the nipple 16 has been over inserted the inventor has devised three further versions of the invention involving the contact of the opposing bell faces 23 these will be applicable in different situations since trenchless installation of the pipeline is identical for all variants they will be described now and the common installation procedure afterwards it will be understood that relative movement between bell faces 23 during push or pull installation may result in abrasion though likely insufficient to cause damage because bell faces of standard.