DRAINAGE 



from both sides, but there is less duplication of 

 work when the main can be at one side of the wet 

 land. Branches of the main may be needed to 

 reach remote parts of the area. 



The Laterals. Small lines of tile are used to 

 bring the water to the main when the wet land 

 extends beyond, the influence of the main. The 

 distance between these laterals depends upon 

 their depth and the nature of the land. A tight 

 clay soil will not let water pass laterally more than 

 a rod or 20 feet, compelling the placing of the 

 drains not over 40 feet apart, while an open soil 

 may permit a distance of 60 or more feet between 

 laterals. 



Size of Tile. The size of the main depends 

 upon the area that eventually may be drained, 

 the amount of overflow from higher land, the 

 nature of the soil, and the grade of the drain. It 

 is a common mistake to make the main too small 

 because the drainage immediately contemplated 

 is less than that which will be desired when its 

 value is known. In the determination of the size 

 the judgment of an expert is needed, and if this 

 cannot be had, the error should be on the side of 

 safety. If the main will not be required to carry 

 overflow from other land, and has a fall of 3 inches 

 B [241] 



