4 BULLETIN 1067, U. S. DEPARTMENT OF AGRICULTURE. 
and the velocity in turn depends upon the diameter or area of the 
pipe at the two ends. The larger the area at these ends the less will 
be the velocity and energy loss, and vice versa. For this reason the 
practice, formerly common, of designing the suction and discharge 
pipes to have the same diameter throughout is now being very 
generally abandoned, though occasionally descriptions of such plants, 
in which the fundamental laws of hydraulics are disregarded, find 
their way into the technical press. 
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Diam. of Opening, Suction and Discharge 
Fig. 1.— Gain in . fficiency due to expanding suction and discharge pipes. 
Until lately the entrance loss has usually been estimated at 0.93 
of the velocity head at the entrance. Bulletin 96 of the Engineering 
Experiment Station, University of Illinois, contains evidence that 
this coefficient is too high and suggests a value of 0.62. The dis- 
charge loss is equal to the velocity head at the end of the discharge 
pipe. If the pipes are round and the diameter be doubled at the 
suction and discharge ends, the areas will be multiplied by 4 ; and 
with Dumping at a constant rate there will be entrance and dis- 
