LAND DEAINAGE 



37 



difficulty of forming a good joint. Horseshoe tile are even more 

 undesirable for the same reason. 



Impervious walls are especially important in any cold region 

 where the tile is' likely to freeze in the ground. The degree of 

 porosity that may be found in so-called, soft tile does not add 

 to their efficiency as drains, since water enters the drain through 

 the joints between the 

 tile. On the other 

 hand, the walls of a 

 tile may be so porous 

 as to take up as much 

 as twenty per cent of 

 water in the minute 

 capillary pores, and 

 when this freezes the 

 wall of the tile is 

 ruptured, and if the 

 process is repeated 

 enough times the tile 

 will crumble to pieces. 

 Even one or two such 

 weak pieces in a line 

 of drains may jeo 

 pardize the system 

 without any corre- 

 sponding benefit. 



The choice between, 

 good clay tile and 

 concrete tile turns 

 primarily on this 

 point of the porosity 

 of the walls. Unless 

 very carefully made, 

 the concrete tile is 

 likely to be the more 

 porous. If concrete tile are used, there should be added to the 

 cement about ten per cent of its volume of hydrated lime, which 

 will make the walls more impervious. 



Joints. — The construction of the joints is a critical part of 

 the system. Imperfect form of the ends of the tile will usually 

 make it easy to leave an opening one-sixteenth to as much as 

 one-quarter of an inch wide. The larger opening should be on 

 the under side. The more the soil in contact with the tile has 



Fig. 14. — The most common types of drainage tile and 

 other materials used for land drainage: 



1. Cobblestones with smaller pieces of stone on 



top. 



2. Flat stones placed face to face and parallel 



to line of ditch. 

 3 and 4. Throated drains constructed of flat 



stones used in difi'erent ways. 

 Pole drain. 



Triangular box drain. 

 Square box drain. Note construction for 



admission of water along lower edge. 

 Horseshoe tile laid on a board. 

 Horseshoe tile, bottom attached. 

 Single sole tile with round opening. 

 Double sole tile. 

 Hexagonal tile. 

 Round tile. 



Y-shaped junction piece. 

 Elbow piece. 



— Tslew York State College of Agriculture. 



5. 

 0. 



7. 



S. 



n. 



10. 



11. 



12. 

 13. 

 14. 

 15. 



