Water tank ,free board, Buffer

Readers ,

Before we take up an actual case study for the water tank size, these are a few clarifications .

Please refer to the following articles :

1.Water tank capacity

2. Water tank size

This is  the additional information :                                                                                                                                           1.Free board : This is a space kept between the top of water level and the bottom of the roof slab of the water tank. Or , the depth between the overflow pipe and the base of the roof slab. Or in another words , what is the clearance maintained between the maximum water level and the roof slab.                                                                  You shall ask me what is the basic purpose of this extra space ?                                                                              These are the objectives : 

  • Safety : During maintenance if a person is inside and if the cover is closed . Then the person can survive by keeping the head in the space between the roof slab and water .
  • Air ventilation : There shall always be free & fresh air on the top of water.
  • Preventing the water from touching the top slab : The space shall prevent the continuous immersion of the roof slab in the tank water .thus we are preventing water from getting polluted.

Maintain a Free board of 250 mm to 300 mm normally .

Therefore , while calculating the height of the water tank , add this 250 mm to 300 mm in the height of the water.


2. Buffer capacity:

While calculating the water tank size, always add at least 100 mm to 150 mm in the height of the water tank { Apart from the 250 mm to 300 mm for the free board }.

The purpose is like this .

In every water tank , there shall always be a tendency for the silt to get deposited in the bottom.

If you keep the delivery pipe exactly at the base, then the silt shall keep flowing through the pipe and shall enter the household through he taps. To prevent this , it is better to fix the delivery pipe at least 100 mm to 150 mm above the base slab of the water tank.



5 thoughts on “Water tank ,free board, Buffer”

  1. For a country home in Konkan having a 25 ft by 30 ft span, how many RCC column would be needed, and what will be the beam size? Will it need 6 TMT bars, say considering a foundation of 5 ft and an elevation of 12 feet. Would a 9″ x 12″ column suffice. Also what the beam for a G+1 construction. For roof, I am looking at I-Beam structure with fibreglass or Bitumen tiles like those of the onduline brand. Thanks & Regards.


    1. You have posed a good question.
      However , its not really possible for me to provide a design based on these details.
      Its a very responsible job and needs lots of inputs.
      May be a competent architect /consultant of your region can help you with this.


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