1828 



The Cornell Reading-Courses 



SIZE OF TILE 



The size of tile will, of course, vary with the area drained, and with the 

 grade and presence of surface and underground courses. The tendency 

 of the day is to increase rather than decrease the minimiim size of the 

 tile used. From the minimum size the tile will increase in size according 

 to the extent of the system. It is now not uncommon for tile as large as 

 two feet in diameter to be used. Three-inch tile in lines not more than 

 six hundred feet long are usually best for lateral drains. For drains up 

 to fifteen hundred feet in length, four-inch tile may be used, provided 

 the grade is not less than four inches per hundred feet. It is difficult to 

 make an exact statement concerning the proper size of main drains. In 

 general they should be capable of removing one fourth of an inch of water 

 from the drainage area in twenty-four hours. Treatises on drainage give 

 tables and formulce by which these relations may be calculated. An 

 increase in the grade increases the rate of flow of water. Doubling 

 the grade increases the carrying capacity of the drain about one third. 

 The following figures give some idea of the area of land drained by some 

 common sizes of tile when laid at difiEerent grades: 



Number of Acres from Which One Fourth Inch of Water Will Be Removed in 

 Twenty-four Hours by Outlet Tile Dr.\insof Different Diameters and Dif- 

 ferent Lengths with Different Grades 



ANGLE OF JUNCTION 



Drains should join at an acute angle rather than at a right angle. In 

 other words, the union of two lines of tile should have the Y rather 

 than the T form, in order to prevent the accumulation of sediment where 

 the two streams of water come together. If the arrangement of the 

 laterals is at right angles to the main, the laterals may be curv^ed in 

 the last rod of their course. The union should be made at the center of 



