86 



LAND DRAINAGE 



eral statements are quoted from C. G. Elliott, recognized 

 as one of the foremost drainage engineers in this country. 

 These statements apply to average conditions : 



" When drains are laid so that there shall be a fall of 3 

 inches in 100 feet, a 3-inch tile will drain 5 acres, and 

 should not be of greater length than 1000 feet. 



TABLE VI 



RELATION OF SIZE OF TILE AND FALL TO CAPACITY TO CONVEY 



WATER 



" These are maximum capacities where the drain does 

 not exceed 1000 feet in length. 



" A long drain has a less carrying capacity than a short 

 drain of the same size laid upon the same grade." 



It is not difficult to see that if a long drain is to be laid, 

 and especially if this drain is a main receiving water from 

 laterals or other sub-mains, it will be necessary, from time 

 to time, to increase the size of the tile laid as the drain 

 approaches the outlet. Fig. 32 illustrates this point. 



By giving careful attention to the capacity of the 

 various sizes, it is possible to exercise considerable economy 

 in the use of tile laid in any system. 



The tendency of the day, according to Fippin, is to 

 increase rather than decrease the minimum size of the 



