the riser inlet is only about 3 u2032 extension rods may be only 2 u2032 in length the body 61 is generally cylindrical in configuration and is shown in fig7 11 it has a front face 77 a back face 78 and an outer side surface 62 the outer side surface 62 has an outer diameter that is slightly less than the inner diameter of the pipe 2 being worked in so that an annular clearance or space 63 is defined therebetween the body 61 forms a plurality of through holes 65 a plurality of threaded recesses 67 a first port 69 for coupling a first monitoring conduit 161 to the body and a second port 71 for coupling a second monitoring conduit 163 to the body it further forms a central bore 73 extending therethrough the central bore 73 is provided through the body 61 to allow the vent rod 311 to extend therethrough the diameter of the body bore 73 is slightly greater than the outer diameter of the vent rod 17 as a result the body 61 is slidable on the vent rod 311 as shown in fig9 the body 39 s first port 69 connects with a first channel 91 extending radially out to the body 39 s circumferential surface 62 at the front end of the body 61.