How to design a circular water tank?/ How to calculate the dimensions of circular water tank?

 Let us design a circular water tank for a hostel of  30 persons as shown below.

According to BIS standard IS 1172-1993,  the average water consumption per head for hostels in India is 135 liters./day

The volume of water required ( in liters ) per day for 30 persons

   = [ per capita consumption /day × no. of persons.]

   = [ 135 liters × 30 nos.]

   = 4050 liters.

Now, let us build a water tank having a 2m. height as shown below.

A. Method - 1:

As you know, 

The volume of the water tank

V1 = [π ×( D2÷4) ×H ]

      = [ 3.142 ×( D2÷4)  × 2m. ]

Here, the volume of the water tank is equal to the vol. of water consumed /day. Let us add 15% extra in the tank volume for the sump & emergency needs.

So, the required volume ( V ) 

 = [water consumption/day + 15% of daily consumption]

 = [ 4050 liters + {( 15 ÷ 100) × 4050 liters}]

= [ 4050 liters. + 607.5 liters ]

= 4657.50 liters.

As you know, 

  1 cu m. = 1000 liters

  So, the vol. V of the water tank in cu m.

   = [ 4657.50 ÷ 1000 ] cu m.

   = 4.658 cu m.

Now,    

           V =   [π ×( D2÷4) ×H ]

     4.658cu m. = [ 3.142 ×( D2÷4)  × 2m. ]

  4.658cu m. = [ 6.284m ×( D2÷4) ]

   4.658cu m. = [ 1.571m. × D2 ]

By cross multiplication,

D2 = [4.658 cu m. ÷ 1.571m.]

              = 2.965 sq m.

  D = √2.965

      = 1.722m.

The inner diameter of the circular water tank should be 1.722m.

Note :

If you want to store the water for the 2days requirement, then you have to double the water tank vol. for the calculation purpose.

For Eg., Let us take 2V instead of V in the calculation.

 2V =   [π ×( D2÷4) ×H ]

   [2 × 4.658cu m.] = [ 3.142 ×( D2÷4)  × 2m. ]

  9.316 cu m. = [ 6.284m ×( D2÷4) ]

   9.316 cu m. = [ 1.571m. × D2 ]

By cross multiplication,

D2 = [9.316 cu m. ÷ 1.571m.]

              = 5.93 sq m.

  D = √5.93

      = 2.435 m.

The inner diameter of the circular water tank should be 2.435m.

B. Method-2:

Let us assume the ideal required dimensions of the tank is as shown in the drawing.

Given data:

   Inner Diameter = D.

   Inner height H =  1.5 × diameter = 1.5D

The required vol. of water tank 

    = 4.658 cum. (as calculated above. )

Now,

 V =   [π ×( D2÷4) ×H ]

     4.658cu m. = [ 3.142 ×( D2÷4)  × 1.5D. ]

     4.658cu m. = [ 4.713D ×( D2÷4) ]

     4.658cu m. = [ 1.178 × D3 ]

By cross multiplication,

D3 = [4.658 cu m. ÷ 1.178]

              = 3.954 cum.

  D = [∛ 3.954 cum.]

      = 1.581m.

Height H = 1.5D

                = [1.5  × 1.581]

                = 2.372m.

The dimension of the circular water tank will be as shown in the below drawing.

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Thank you for going through this article❤. Have a good day 😄.

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