104 Bulletin 86 



when two or three feet of earth have have been placed over the pipe. 

 No extensive flooding should be done, however, without first filling 

 the pipe line, as there is danger of floating an empty pipe line up- 

 ward and breaking the joints. If the flooding is not feasible, the 

 soil can be tamped in until the backfill is above the center of the 

 pipe. One contractor has his backfiller straddle the pipe and as he 

 pulls the soil in with a shovel he continually tramps upon it. In the 

 drainage districts of the Middle West usually the bed of the trench 

 is shaped semi-circular to fit the drain tile and it is considered poor 

 practice to lay the tile on a flat bed. The soils are, of course, heavy 

 and wet, and there are no convenient facilities for flooding as there 

 are along an irrigation pipe line. A 2-inch layer of sand is some- 

 times spread on a clay trench bottom to serve as a bed for the pipe. 

 In case the pipe has lain in the pipe yard until it is thoroughly 

 dry, it is a good precautionary measure to run water over a shallow 

 backfill before or at the same time that the water is turned into the 

 line, in order to guard against failures such as described on page 110. 



METHODS OF LAYING 



Cement pipe with tongue and groove joints are laid in the trench 

 with great facility. The mortar used for this purpose should be 

 rich. It is usually mixed with two parts of sand to one ot cement. 

 Hydrated lime adds to the smooth working qualities of the mortar, 

 making the mortar "fat," but it is not essential. It was used at Con- 

 tinental for a time, then discontinued, and afterwards used again. 

 Six or eight pounds per sack of cement is the proper amount to use. 



The pipe are distributed along the trench by team, and are 

 handed down and stood on the groove ends in the trench. A gal- 

 vanized iron form about 12 inches long, called the laying core, is 

 inserted in the groove end, projecting about three inches. The space 

 between the form and the groove is then filled with mortar, and ad- 

 ditional mortar is placed under the tongue in the trench. The joint 

 of pipe is tipped over and jointed quickly. While a helper raises it 

 slightly with a pair of pipe tongs, or a leather strap, the pipe layer 

 stooping down gives the pipe a quick thrust which closes the groove 

 tightly over the tongue. Small sizes are handled by the layer with- 

 out a helper. The laying core is then drawn out through the end 

 of the pipe and placed in the groove end of the next pipe. The pipe 

 layer reaches in with a long-handled brush and smooths the joint. 

 A third man, following along in the trench, spreads a band of mor- 

 tar about three inches wide over the joint. This is called banding. 

 It is omitted sometimes on pipe lines of small pipe that are to be 



