EXAMPLES 287 



yards to 8 inches. A re-entrant mouthpiece is fitted at the entrance, 

 while discharge takes place directly into the side of the lower reservoir 

 at a depth of 6 feet below the surface. If the difference in the surface 

 level in the reservoirs is 10 feet, determine the discharge in gallons per 

 minute. /= '005. 



Answer. 121 gallons per minute. 



(2) A gate valve in a 12-inch cylindrical C. I. pipe is lifted through f 

 of its full opening. Determine the equivalent length of a straight pipe 

 offering the same resistance. /= "005. 



Answer. / = 276 feet. 



(3) Two reservoirs of 80,000 and 10,000 square feet area are connected 

 by a 6-inch pipe, 500 feet long. Initially, the difference of surface level 

 is 16 feet. Determine how soon the level in the two reservoirs will be 

 the same. Take / = '0075. 



Answer. About 69 hours. 



(4) Two reservoirs, surfaces 15 and 25 feet above a common datum 

 feed through a 12-inch and an 18-inch pipe respectively, into a common 

 24-inch pipe at a height 5 feet above datum level, while this in turn 

 feeds a reservoir whose surface level is taken as datum. If the lengths 

 of the 12-inch, 18-inch, and 24-inch pipes are respectively 1,000 feet, 1,500 

 feet, and 2,000 feet, determine the velocity of flow in and the discharge 

 through each pipe, neglecting all losses of head except those due to 

 friction. Also determine the pressure at the junction of the three pipes. 

 Take/ = '005. 



12 in. pipe, v = 4'62 f.s. Q= 3'62 c.f.s. 

 , 18 v = 7'22 f.s. Q = 12-76 c.f.s. 

 ^ t; = 5-21f.s. Q = 16-88 c.f.s. 

 Pressure at junction = 3'03 ft. of water. 



/ H 



(5) Assuming Q a V -r- d 2 ' 68 determine the discharge from a 12-inch 



pipe, if a similar 8-inch pipe of half the length gives a discharge of 

 10,000 gallons per hour under the same head. 



Answer. 20,153 gallons per hour. 



(6) A pumping engine supplies water at a pressure of 75 Ibs. per 

 square inch through a short pipe 20 inches diameter to a hydrant box, 

 from which it is discharged by four parallel nozzles 2 inches in diameter. 

 Taking the coefficient of loss in the nozzles to be '03, determine the 

 water horse-power of the engine. 



Answer. 181 horse-power. 



(7) The difference of surface level in two reservoirs which are connected 



