WATER CONDUCTORS 



119 



Hydraulic Gradient. The hydraulic gradient is, strictly 

 speaking, a line representing atmospheric pressure conditions, 

 although it may also conveniently be used as a graphical repre- 

 sentation of the internal pressures in a pipe line at any point. 

 It may also be defined as the line, the vertical distance between 

 which and the center of the pipe gives the pressure heads at 

 the respective points. For example, referring to Fig. 59A, the 

 hydraulic gradient or grade line is a line through the points to 



FIG. 59A. Hydraulic Gradient. 



which the water levels would rise if piezometer tubes were inserted 

 along the pipe, as shown. The line will be approximately straight 

 when the head is lost uniformly along the pipe, that is, if the 

 size and surface of the entire length of pipe is the same. 



The grade line should be drawn from a point A near the upper 

 water-level, the distance AB being equal to the velocity head 

 plus the entrance head, to a point at the end of the pipe. For 

 a pipe discharging freely in the air this would be the center of 



