CHAPTER IX. 

 FLOW OF WATER THROUGH PIPES. 



Before taking up the subject of the size of drains it 

 is proposed to outline briefly that branch of hydraulics 

 which relates to the flow of water through pipes, in 

 order that the beginning engineer may have the basis 

 upon which to study the flow of water through tile 

 drains. While there have been very elaborate investi- 

 gations made upon this subject, it is only necessary in 

 this connection to outline the facts without entering 

 into a full analytical discussion of the matter. 



It should be borne in mind by those who are plan- 

 ning drainage works that gravity is the sole cause of 

 flow in water. The flow of water in a drain of whatever 

 kind is owing to the inclination of the surface of the 

 fluid. The same universal force causes unsupported 

 bodies to fall vertically, a ball to roll down an incline, 

 and water to flow along a channel or through a pipe. 

 The formula used to express the theoretical velocity due 

 to gravity is 



where v == velocity in feet per second; 

 g = accelerating force of gravity ; 

 h = space through which the body falls. 



It has been found by experiment that a body in 

 vacuum at the level of the sea passes through a space of 



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