For high rise building, the dimension of a water tank along with drawings are provided from the architect office. But for small residential building, we need to calculate by itself. In this article, we will discuss how to calculate rectangular water tank size and capacity.

The volume of Water Requirement

As per IS code, a person needs 135 litres water per day for daily use.

Drinking – 5 Litre

Cooking – 5 litres

Bathing and Toilet – 85 litres

Washing clothes and Utensils – 30 litres

House Cleaning – 10 litres

Calculation Of tank Size and Capacity

We will calculate for a typical family having 4 members.

Total water requirement = 135 x 4 = 540 litres

To calculate the size of the water tank we must know any  one of the following:

Length or width or depth of the tank.

From the formula of volume of water

m3 = 1000 litres

1 litre = 0.001 m3

We are requiring 540-litre water

 540 litres = 0.54 m3

Let us assume the depth of the water tank is 0.6 m.

 Area of tank = 0.54/0.6 = 0.9 m2

L x B = 0.9 m2

Now if you know the length or breadth you can put the value on the above formula.

otherwise, take the length as 2 times of B.

 L = 2B

2B x B = 0.9 m2

B2 = 0.45

B = 0.67

 L = 2 x 0.67 = 1.34 m

So For 540 litre water tank size

Length (L) = 1.34 m

Breatdh (B) = 0.67 m

Depth (D) = 0.6 m

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