which may be made of stainless steel the number of inserts used depends on the length of cover 28 each insert is preferably a strip of rectangular and uniform crossection the strip or insert is intended to fit tightly between one side of the female dovetail seat 26 and the surface 32 of the cover 28 each insert has a plurality of spaced holes 35 therethrough the holes are accessible from the top when the insert 34 is in seat 26 a plurality of chain lengths 36 at each end of an insert are welded thereto and to section 11 the chains 36 support the inserts when they are out of the seat 26 as shown in fig1 with cover 28 and inserts 34 mounted in seat 26 tapping cover 28 at the tending side will force the cover and insert toward the driving side to tightly wedge same in seat 26 providing an airtight connection therewith any vacuum applied to section 11 therefore will draw water through the felt passing over cover 28 through slotted passages 29 and 30 therein and through slots 14 in bar 12 into the interior of pipe 10 of course cover 28 and the felt 37 in moving contact therewith must fit smoothly as mentioned previously if there are wear grooves in the top of cover 28 air can move therethrough and into the pipe section 11 defeating the goal of drawing the water from the felt because.