DRAINAGE 297 



a good junction made with the tile. Where practicable the 

 last tile should extend 2 inches into the outlet protection. If 

 the water begins running around the outside of the outlet, it is 

 likely to be washed out. Until the trenches have thoroughly 

 settled and the slope of the ditch has set in grass, the loose 

 dirt will slip down in front of the outlet. If a structure 

 in the nature of a wall is built at the outlet, there will be 

 less trouble from this source. During the period of the dry 

 season grass and leaves will blow through the screen, and 

 when the water begins to run, this drift will wash down and 

 lodge against the screen, causing an obstruction. The outlet 

 will thus require some attention to keep it in working order. 



Cleaning out tile. When tile becomes clogged, the approxi- 

 mate location of the obstruction may be determined shortly 

 after a rain. The ground will dry out up to the point where 

 the tile is not working, while above the obstruction the soil 

 will be filled with water. The line between the wet and dry 

 soil will determine the location of the obstruction. Holes 

 can be dug down to the tile and two or three joints taken out. 

 Lath can be inserted one at a time and fastened by small 

 nails and run back into the tile a hundred feet or more. If 

 other holes are dug, connections may be made underground 

 with the lath and these be worked back and forth; if there 

 is some water in the tile, silt and other deposits may be 

 stirred up and the water will carry them out. The lath can 

 be carried down through the line of tile by means of holes dug 

 at sufficient intervals so that the string of lath will pass from 

 one to another. A bunch of hay or straw tied in a bag and 

 pulled through the tile will clean it out effectively if the 

 deposits are not too solid. 



Injury by freezing. A good quality of tile will not be 

 affected by freezing if laid to grade so that water cannot 

 stand in the tile. Tile holding water to a depth equal to 

 one-fourth of its diameter can be frozen many times without 

 serious injury, but if the water reaches the horizontal 

 diameter, or the tile is three-fourths full of water, freezing 



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