Water is to be supplied to the inhabitants of a college campus through a supply pipe. The following data is given: Distance of the reservoir from the campus = 3000 m Number of inhabitants = 4000 Consumption of water per day of each inhabitant = 180 liters Loss of head due to friction = 18 m Co-efficient of friction for the pipe, f = 0.007 If the half of the daily supply is pumped in 8 hours, determine the size of the supply main.

 Water is to be supplied to the inhabitants of a college campus through a supply pipe. The following data is given: 

Distance of the reservoir from the campus = 3000 m 

Number of inhabitants = 4000 

Consumption of water per day of each inhabitant = 180 liters 

Loss of head due to friction = 18 m 

Co-efficient of friction for the pipe, f = 0.007 

If the half of the daily supply is pumped in 8 hours, determine the size of the supply main. 

Solution:

 Distance of the reservoir from the campus = 3000 m 

Number of inhabitants = 4000

Consumption of water per day of each inhabitant 

                                                   = 180 liters = 0.18 m3 

Therefore total supply per day = 4000*0.18 = 720 m3 

 Since half of the daily supply is pumped in 8 hours, therefore maximum flow for which the pipe is to be designed,

                                                 Q = 720/ (2*8*3600) 

                                                     = 0.0125 m3 /s

 Loss of head due to friction,

 hf = 18 m 

and Co-efficient of friction, f = 0.007 

Diameter of the supply line, D:

 Using the relation:

 hf = 4fLV2 /2gD 

velocity of flow, V = Q/A=0.0125/ (π*D2 /4) = 0.0159/D2

 By substitution for loss of head due to friction 

 18=4*0.007*3000*(0.0159/D2 ) 2 /D*2*9.81 

or D5 = (4*0.007*3000*0.01592 )/(18*2*9.81) 

                                      = 6.013*10-5 

 Size of the supply main, D = 0.143 m = 143 mm