Measuring The Volume Of Water In A Water Tank

Measuring the volume of water in a tank

Measuring The Volume Of Water In A Water Tank

Future Wars will be fought over Water

Often referred to as the water wars thesis, it suggests that future wars will be fought over water, not oil. Even in countries with proper natural water supply, water scarcity is not uncommon. Every day, usable water is becoming scarce and water costs are rising. 

This economic water scarcity arises due to a lack of water infrastructure or due to the poor management of water resources. This needs to be solved at the local as well as central level. The common people need to be interested in conserving and managing their water. 

Water Management Begins With Measurement. 

For any water saving practices to become effective, it is important to first measure the volume of water received, used and available. 

Volume of water flowing through a pipe can be measured with equipment such as a digital flow meter. The equipment that can be used for water volume measurement has been described in this previous blog. Other equipment such as water level indicator or water level sensor typically give only an indication of the water height.

Read here previous blog- Equipment for Water Management and Measurement

Today, we shall take a look at the different ways in which tanks are constructed and connected and how to measure the volume of water in a tank based on the same information.

Tank Volume MeasurementOverview

Generally speaking, the overall physical tank volume is already known beforehand. It is mentioned in the M. E. P. architectural diagrams constructed by the architects. If such a diagram is not available, one can always calculate the volume by measuring the dimensions of the tank and using the following formulae.

VOLUME = LENGTH X BREADTH X HEIGHT (for a rectangular tank) or 

VOLUME = AREA OF BASE X HEIGHT (for a cylindrical tank)

water Tank Volume Measurement

Measurement of the volume of water that a tank can hold is NOT as straightforward as measuring the physical volume of the tank. When calculating the volume of water in a tank, we need to consider many things:

Water Volume Measurement

  • Shape of the Tank

Volume is dependent on the shape of the tank. If the tank has a regular shape, it is easy to calculate water volume as per the following formulae

For a Rectangular/ Cuboidal Tank


For a Cylindrical Tank


Water Volume Measurement

Irregularly Shaped Tanks

We hardly ever find tanks that have irregular shapes. This may also be due to aesthetic reasons, in order to conform to the overall theme of the project’s construction or due to various other reasons. 

In such cases, we can split the shapes into multiple regular shaped components and determine the volume of each individual shape. All these volumes can then be added together to get an overall volume. Here is an example of an irregular tank and its volume calculation.

For more details- WaterApp

water tank
  • Height and Location of the Overflow Pipe

Overflow pipes are installed in tanks so as to give a smooth, structured passage of water in case the tank overflows. When a tank is equipped with an overflow outlet, another pipe can be connected to it. This way, excess water can be drained into another tank or storage location so that the water does not get wasted.

When a tank has an overflow outlet, water can be stored only until the height of that outlet, as shown in the diagram. 


water volume of a tank with overflow pipe
  • Usable Volume: Accounting for Fire Tank Volume

Modern tanks are constructed so as to take into account fire safety as well. Sometimes there is a separate storage tank for storing the water that may be needed during a fire emergency. Typically, this tank fills up first and its overflow is drained into the domestic tank.

In other cases, the main tank is constructed in a way that a separate compartment has been created for storing the dead stock of fire water. All these constructions are done to ensure that the fire tank portion is always filled up before the domestic tank and that it never gets empty.

In these cases, to get an accurate estimate of the volume of water available, one also needs to calculate the volume of USABLE water in addition to the volume of TOTAL water stored.

Let us take a look at these diagrams to understand better:

volume of TOTAL water stored
Dead stock maintained for fire
  • Internal Partitions

Generally residential projects are constructed such that one or two underground tanks store and supply water to multiple overhead tanks of multiple buildings. Hence the underground tanks are huge with large capacity. Instead of having individual walls for tanks, the tanks are built with separate interconnected partitions. 

This makes it possible to store water from different sources in different compartments (for e.g., drinking water which comes from the corporation can be stored in a separate compartment while domestic water from tankers, bore or other sources can be stored separately without any mix up between the two).

Also read- Water Saving Tips for Housing Societies

At the same time, the tanks are connected from within via pipes or valves between the partitions. This way, excess water from one section can be emptied into the other section. For e.g. excess drinking water can be let into the domestic tank. 

One advantage of this type of construction is that one water level indicator or sensor system can be used for all the tanks as the level of water in all the partitions is the same.

In such cases, it is difficult to take measurements from outside. It’s best if one can receive a construction diagram from the builder.

Volume can be calculated in the following way:

water tank connected with internal partition
  • Connected Tanks

As explained above, there are many advantages to connecting tanks together.

  1. Overflow of one tank can be let into the other tank instead of water going waste
  2. If the tanks are connected at the bottom, the level of all tanks would be the same and one water level indicator is sufficient for multiple tanks.
  3. When tanks are connected in smart ways; it is possible to reserve a portion of the water for fire emergencies and yet have enough water available for domestic use.
connected water tank

We see that water volume measurement is not as simple as multiplying length, breadth and height. Before finding the volume, one must first understand the connections and interconnections within the tanks. 

In our next blog we will go deeper into the quality of water stored in these tanks, both, overhead and underground tanks.

Measuring The Volume Of Water In A Water Tank

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